Watson's Biblical & Theological Dictionary 
That nearly all the Pagan nations of antiquity, says Bishop Tomline, in their various theological systems, acknowledged a kind of Trinity, has been fully evinced by those learned men who have made the Heathen mythology the subject of their elaborate inquiries. The almost universal prevalence of this doctrine in the Gentile kingdoms must be considered as a strong argument in favour of its truth. The doctrine itself bears such striking internal marks of a divine original, and is so very unlikely to have been the invention of mere human reason that there is no way of accounting for the general adoption of so singular a belief, but by supposing that it was revealed by God to the early patriarchs, and that it was transmitted by them to their posterity. In its progress, indeed, to remote countries, and to distant generations, this belief became depraved and corrupted in the highest degree; and he alone who brought "life and immortality to light," could restore it to its original simplicity and purity. The discovery of the existence of this doctrine in the early ages, among the nations whose records have been the best preserved, has been of great service to the cause of Christianity, and completely refutes the assertion of infidels and skeptics, that the sublime and mysterious doctrine of the Trinity owes its origin to the philosophers of Greece. "If we extend," says Mr. Maurice, "our eye through the remote region of antiquity, we shall find this very doctrine, which the primitive Christians are said to have borrowed from the Platonic school, universally and immemorially flourishing in all those countries where history and tradition have united to fix those virtuous ancestors of the human race, who, for their distinguished attainments in piety, were admitted to a familiar intercourse with Jehovah and the angels, the divine heralds of his commands." The same learned author justly considers the first two verses of the Old Testament as containing very strong, if not decisive, evidence in support of the truth of this doctrine: Elohim, a noun substantive of the plural number, by which the Creator is expressed, appears as evidently to point toward a plurality of persons in the divine nature, as the verb in the singular, with which it is joined, does to the unity of that nature: "In the beginning God created;" with strict attention to grammatical propriety, the passage should be rendered, "In the beginning Gods created," but our belief in the unity of God forbids us thus to translate the word Elohim. Since, therefore, Elohim is plural, and no plural can consist of less than two in number, and since creation can alone be the work of Deity, we are to understand by this term so particularly used in this place, God the Father, and the eternal Logos, or Word of God; that Logos whom St. John, supplying us with an excellent comment upon this passage, says, was in the beginning with God, and who also was God. As the Father and the Son are expressly pointed out in the first verse of this chapter, so is the Third Person in the blessed Trinity not less decisively revealed to us in Genesis 1:2 : "And the Spirit of God moved upon the face of the waters:" "brooded upon" the water, incubavit, as a hen broods over her eggs. Thus we see the Spirit exerted upon this occasion an active effectual energy, by that energy agitating the vast abyss, and infusing into it a powerful vital principle.
Elohim seems to be the general appellation by which the Triune Godhead is collectively distinguished in Scripture; and in the concise history of the creation only, the expression, bara Elohim, "the Gods created," is used above thirty times. The combining this plural noun with a verb in the singular would not appear so remarkable, if Moses had uniformly adhered to that mode of expression; for then it would be evident that he adopted the mode used by the Gentiles in speaking of their false gods in the plural number, but by joining with it a singular verb or adjective, rectified a phrase that might appear to give a direct sanction to the error of polytheism. But, in reality, the reverse is the fact; for in Deuteronomy 32:15; Deuteronomy 32:17 , and other places, he uses the singular number of this very noun to express the Deity, though not employed in the August work of creation: "He forsook God," Eloah; "they sacrificed to devils, not to God," Eloah. But farther, Moses himself uses this very word Elohim with verbs and adjectives in the plural. Of this usage Dr. Allix enumerates many other striking instances that might be brought from the Pentateuch; and other inspired writers use it in the same manner in various parts of the Old Testament, Job 35:10; Joshua 24:19; Psalms 109:1; Ecclesiastes 12:3; 2 Samuel 7:23 . It must appear, therefore, to every reader of reflection, exceedingly singular, that when Moses was endeavouring to establish a theological system, of which the unity of the Godhead was the leading principle, and in which it differed from all other systems, he should make use of terms directly implicative of a plurality in it; yet so deeply was the awful truth under consideration impressed upon the mind of the Hebrew legislator, that this is constantly done by him; and, indeed, as Allix has observed, there is scarcely any method of speaking from which a plurality in Deity may be inferred, that is not used either by himself in the Pentateuch, or by the other inspired writers in various parts of the Old Testament. A plural is joined with a verb singular, as in the passage cited before from Genesis 1:1; a plural is joined with a verb plural, as in Genesis 35:7 , "And Jacob called the name of the place El- beth-el, because the Gods there appeared to him;" a plural is joined with an adjective plural, Joshua 24:19 , "You cannot serve the Lord; for he is the holy Gods." To these passages, if we add that remarkable one from Ecclesiastes, "Remember thy Creators in the days of thy youth," and the predominant use of the terms, Jehovah Elohim, or, the "Lord thy Gods," which occur a hundred times in the law, (the word Jehovah implying the unity of the essence, and Elohim a plurality in that unity,) we must allow that nothing can be more plainly marked than this doctrine in the ancient Scriptures.
Though the August name of Jehovah in a more peculiar manner belongs to God the Father, yet is that name, in various parts of Scripture, applied to each person in the holy Trinity. The Hebrews considered that name in so sacred a light, that they never pronounced it, and used the word Adonai instead of it. It was, indeed a name that ranked first among their profoundest cabbala; a mystery, sublime, ineffable, incommunicable. It was called tetragrammaton, or the name of four letters, and these letters are jod, he, vau, he, the proper pronunciation of which, from long disuse, is said to be no longer known to the Jews themselves. This awful name was first revealed by God to Moses from the centre of the burning bush; and Josephus, who, as well as Scripture, relates this circumstance, evinces his veneration for it, by calling it the name which his religion did not permit him to mention. From this word the Pagan title of Iao and Jove is, with the greatest probability, supposed to have been originally formed; and in the Golden Verses of Pythagoras, there is an oath still extant to this purpose, "By Him who has the four letters." As the name Jehovah, however, in some instances applied to the Son and the Holy Spirit, was the proper name of God the Father, so is Logos in as peculiar a manner the appropriated name of God the Son. The Chaldee Paraphrasts translate the original Hebrew text by Mimra da Jehovah, literally, "the word of Jehovah," a term totally different, as Bishop Kidder has incontestably proved, in its signification, and in its general application among the Jews, from the Hebrew dabar, which simply means a discourse or decree, and is properly rendered by pithgam. In the Septuagint translation of the Bible, a work supposed by the Jews to have been undertaken by men immediately inspired from above, the former term is universally rendered Λογος , and it is so rendered and so understood by Philo and all the more ancient rabbins. The name of the third person in the ever blessed Trinity has descended unaltered from the days of Moses to our own time; for, as well in the sacred writings as by the Targumists, and by the modern doctors of the Jewish church, he is styled Ruach Hakhodesh, the Holy Spirit. He is sometimes, however, in the rabbinical books, denominated by Shechinah, or glory of Jehovah; in some places he is called Sephirah, or Wisdom; and in others the Binah, or Understanding. From the enumeration of these circumstances, it must be sufficiently evident to the mind which unites piety and reflection, that so far from being silent upon the subject, the ancient Scriptures commence with an avowal of this doctrine, and that, in fact, the creation was the result of the joint operations of the Trinity.
If the argument above offered should still appear inconclusive, the twenty- sixth verse of the first chapter of Genesis contains so pointed an attestation to the truth of it, that, when duly considered, it must stagger the most hardened skeptic; for in that text not only the plurality is unequivocally expressed, but the act which is the peculiar prerogative of Deity is mentioned together with that plurality, the one circumstance illustrating the other, and both being highly elucidatory of this doctrine: "And God (Elohim) said, Let us make man in our image, after our likeness." Why the Deity should speak of himself in the plural number, unless that Deity consisted of more than one person, it is difficult to conceive; for the answer given by the modern Jews, that this is only a figurative mode of expression, implying the high dignity of the speaker, and that it is usual for earthly sovereigns to use this language by way of distinction, is futile, for two reasons. In the first place it is highly degrading to the Supreme Majesty to suppose he would take his model of speaking and thinking from man, though it is highly consistent with the vanity of man to arrogate to himself, as doubtless was the case in the licentiousness of succeeding ages, the style and imagined conceptions of Deity; and it will be remembered, that these solemn words were spoken before the creation of any of those mortals, whose false notions of greatness and sublimity the Almighty is thus impiously supposed to adopt. In truth, there does not seem to be any real dignity in an expression, which, when used by a human sovereign in relation to himself, approaches very near to absurdity. The genuine fact, however, appears to be this. When the tyrants of the east first began to assume divine honours, they assumed likewise the majestic language appropriated to, and highly becoming, the Deity, but totally inapplicable to man. The error was propagated from age to age through a long succession of despots, and at length Judaic apostasy arrived at such a pitch of profane absurdity, as to affirm that very phraseology to be borrowed from man which was the original and peculiar language of the Divinity. It was, indeed, remarkably pertinent when applied to Deity; for in a succeeding chapter, we have more decisive authority for what is thus asserted, where the Lord God himself says. "Behold, the man is become as one of us;" a very singular expression, which some Jewish commentators, with equal effrontery, contend was spoken by the Deity to the council of angels, that, according to their assertions, attended him at the creation. From the name of the Lord God being used in so emphatical a manner, it evidently appears to be addressed to those sacred persons to whom it was before said, "Let us make man;" for would indeed the omnipotent Jehovah, presiding in a less dignified council, use words that have such an evident tendency to place the Deity on a level with created beings?
The first passage to be adduced from the New Testament in proof of this important doctrine of the Trinity, is, the charge and commission which our Saviour gave to his apostles, to "go and teach all nations, baptizing them in the name of the Father, and of the Son, and of the Holy Ghost,"
Matthew 28:19 . The Gospel is every where in Scripture represented as a covenant or conditional offer of eternal salvation from God to man; and baptism was the appointed ordinance by which men were to be admitted into that covenant, by which that offer was made and accepted. This covenant being to be made with God himself, the ordinance must of course be performed in his name; but Christ directed that it should be performed in the name of the Father, and of the Son, and of the Holy Ghost; and therefore we conclude that God is the same as the Father, the Son, and the Holy Ghost. Since baptism is to be performed in the name of the Father, the Son, and the Holy Ghost, they must be all three persons; and since no superiority or difference whatever is mentioned in this solemn form of baptism, we conclude that these three persons are all of one substance, power, and eternity. Are we to be baptized in the name of the Father, of the Son, and of the Holy Ghost, and is it possible that the Father should be self-existent, eternal, the Lord God Omnipotent; and that the Son, in whose name we are equally baptized, should be a mere man, born of a woman, and subject to all the frailties and imperfections of human nature? or, is it possible that the Holy Ghost, in whose name also we are equally baptized, should be a bare energy or operation, a quality or power, without even personal existence? Our feelings, as well as our reason, revolt from the idea of such disparity.
This argument will derive great strength from the practice of the early ages, and from the observations which we meet with in several of the ancient fathers relative to it. We learn from Ambrose, that persons at the time of their baptism, declared their belief in the three persons of the Holy Trinity, and that they were dipped in the water three times. In his Treatise upon the Sacraments he says, "Thou wast asked at thy baptism, Dost thou believe in God the Father Almighty? and thou didst reply, I believe, and thou wast dipped; and a second time thou wast asked, Dost thou believe in Jesus Christ the Lord? thou didst answer again, I believe, and thou wast dipped; a third time the question was repeated, Dost thou believe in the Holy Ghost? and the answer was, I believe, then thou wast dipped a third time." It is to be noticed, that the belief, here expressed separately, in the three persons of the Trinity, is precisely the same in all. Tertullian, Basil, and Jerom, all mention this practice of trine immersion as ancient; and Jerom says, "We are thrice dipped in the water, that the mystery of the Trinity may appear to be but one. We are not baptized in the names of Father, Son, and Holy Ghost, but in one name, which is God's; and, therefore, though we be thrice put under water to represent the mystery of the Trinity, yet it is reputed but one baptism." Thus the mysterious union of the Father, the Son, and the Holy Ghost, as one God, was, in the opinion of the purer ages of the Christian church, clearly expressed in this form of baptism. By it the primitive Christians understood the Father's gracious acceptance of the atonement offered by the Messiah; the peculiar protection of the Son, our great High Priest and Intercessor; and the readiness of the Holy Ghost to sanctify, to assist, and to comfort all the obedient followers of Christ, confirmed by the visible gift of tongues, of prophecy, and divers other gifts to the first disciples. And as their great Master's instructions evidently distinguished these persons from each other, without any difference in their authority or power, all standing forth as equally dispensing the benefits of Christianity, as equally the objects of the faith required in converts upon admission into the church, they clearly understood that the Father, the Son, and the Holy Ghost, were likewise equally the objects of their grateful worship: this fully appears from their prayers, doxologies, hymns, and creeds, which are still extant.
The second passage to be produced in support of the doctrine now under consideration, is, the doxology at the conclusion of St. Paul's Second Epistle to the Corinthians, "The grace of our Lord Jesus Christ, the love of God, and the fellowship of the Holy Ghost, be with you." The manner in which Christ and the Holy Ghost are here mentioned, implies that they are persons, for none but persons can confer grace or fellowship; and these three great blessings of grace, love, and fellowship, being respectively prayed for by the inspired apostle from Jesus Christ, God the Father, and the Holy Ghost, without any intimation of disparity, we conclude that these three persons are equal and Divine. This solemn benediction may therefore be considered as another proof of the Trinity, since it acknowledges the divinity of Jesus Christ and of the Holy Ghost. The third passage is the following salutation or benediction in the beginning of the Revelation of St. John: "Grace and peace from Him which is, and which was, and which is to come; and from the seven spirits which are before his throne, and from Jesus Christ." Here the Father is described by a periphrasis taken from his attribute of eternity; and "the seven spirits" is a mystical expression for the Holy Ghost, used upon this occasion either because the salutation is addressed to seven churches, every one of which had partaken of the Spirit. or because seven was a sacred number among the Jews, denoting both variety and perfection, and in this case alluding to the various gifts, administrations, and operations of the Holy Ghost. Since grace and peace are prayed for from these three persons jointly and without discrimination, we infer an equality in their power to dispense those blessings; and we farther conclude that these three persons together constitute the Supreme Being, who is alone the object of prayer, and is alone the Giver of every good and of every perfect gift. It might be right to remark, that the seven spirits cannot mean angels, since prayers are never in Scripture addressed to angels, nor are blessings ever pronounced in their name. It is unnecessary to quote any of the numerous passages in which the Father is singly called God, as some of them must be recollected by every one, and the divinity of the Father is not called in question by any sect of Christians; and those passages which prove the divinity of the Son and of the Holy Ghost separately, will be more properly, considered under those heads. In the mean time we may observe, that if it shall appear from Scripture, that Christ is God, and the Holy Ghost is God, it will follow, since we are assured that there is but one God, that the three persons, the Father, the Son, and the Holy Ghost, by a mysterious union, constitute the one God, or, as it is expressed in the first article of the church of England: "There is a Trinity in Unity; and in the unity of this Godhead there be three Persons of one substance, power, and eternity, the Father, the Son, and the Holy Ghost."
The word Trinity does not occur in Scripture, nor do we find it in any of the early confessions of faith; but this is no argument against the doctrine itself, since we learn from the fathers of the first three centuries, that the divinity of the Son and of the Holy Ghost was, from the days of the Apostles, acknowledged by the catholic church, and that those who maintained a contrary opinion were considered as heretics; and as every one knows that neither the divinity of the Father, nor the unity of the Godhead, was ever called in question at any period, it follows that the doctrine of the Trinity in Unity has been in substance, in all its constituent parts, always known among Christians. In the fourth century it became the subject of eager and general controversy; and it was not till then that this doctrine was particularly discussed. While there was no denial or dispute, proof and defence were unnecessary: Nunquid enim perfecte de Trinitate tractatum est, antequam oblatrarent Ariani? But this doctrine is positively mentioned as being admitted among catholic Christians, by writers who lived long before that age of controversy. Justin Martyr, in refuting the charge of atheism urged against Christians, because they did not believe in the gods of the Heathen, expressly says, "We worship and adore the Father, and the Son who came from him and taught us these things, and the prophetic Spirit;" and soon after, in the same apology, he undertakes to show the reasonableness of the honour paid by Christians to the Father in the first place, to the Son in the second, and to the Holy Ghost in the third; and says, that their assigning the second place to a crucified man, was, by unbelievers, denominated madness, because they were ignorant of the mystery, which he then proceeds to explain. Athenagoras, in replying to the same charge of atheism urged against Christians, because they refused to worship the false gods of the Heathen, says "Who would not wonder, when he knows that we, who call upon God the Father, and God the Son, and God the Holy Spirit, showing their power in the unity, and their distinction in order, should be called atheists?" Clement of Alexandria not only mentions three divine persons, but invokes them as one only God. Praxeas, Sabellius, and other Unitarians, accused the orthodox Christians of tritheism, which is of itself a clear proof that the orthodox worshipped the Father, the Son, and the Holy Ghost; and though in reality they considered these three persons as constituting the one true God, it is obvious that their enemies might easily represent that worship as an acknowledgment of three Gods. Tertullian, in writing against Praxeas, maintains, that a Trinity rationally conceived is consistent with truth, and that unity irrationally conceived forms heresy. He had before said, in speaking of the Father, Son, and Holy Ghost, that "there are three of one substance, and of one condition, and of one power, because there is one God:" and he afterward adds, "The connection of the Father in the Son, and of the Son in the Comforter, makes three united together, the one with the other; which three are one thing, not one person; as it is said, I and the Father are one thing, with regard to the unity of substance, not to the singularity of number:" and he also expressly says, "The Father is God, and the Son is God, and the Holy Ghost is God;" and again, "The Father, the Son, and the Holy Ghost, believed to be three, constitute one God." And in another part of his works he says, "There is a Trinity of one Divinity, the Father, and the Son, and the Holy Ghost." And Tertullian not only maintains these doctrines, but asserts that they were prior to any heresy, and had, indeed, been the faith of Christians from the first promulgation of the Gospel. To these writers of the second century, we may add Origen and Cyprian in the third; the former of whom mentions baptism (alluding to its appointed form) as "the source and fountain of graces to him who dedicates himself to the divinity of the adorable Trinity." And the latter, after reciting the same form of baptism, says that "by it Christ delivered the doctrine of the Trinity, unto which mystery or sacrament the nations were to be baptized." It would be easy to multiply quotations upon this subject; but these are amply sufficient to show the opinions of the early fathers, and to refute the assertion that the doctrine of the Trinity was an invention of the fourth century. To these positive testimonies may be subjoined a negative argument: those who acknowledged the divinity of Christ and of the Holy Ghost, are never called heretics by any writer of the first three centuries; and this circumstance is surely a strong proof that the doctrine of the Trinity was the doctrine of the primitive church; more especially, since the names of those who first denied the divinity of Christ and of the Holy Ghost, are transmitted to us as of persons who dissented from the common faith of Christians.
But while we contend that the doctrine of the Trinity in Unity is founded in Scripture, and supported by the authority of the early Christians, we must acknowledge that it is not given to man to understand in what manner the three persons are united, or how, separately and jointly, they are God. It would, perhaps, have been well, if divines, in treating this awful and mysterious subject, had confined themselves to the expressions of Scripture; for the moment we begin to explain it beyond the written word of God, we plunge ourselves into inextricable difficulties. And how can it be otherwise? Is it to be expected that our finite understandings should be competent to the full comprehension of the nature and properties of an infinite Being? "Can we find out the Almighty to perfection," Job 11:7; or penetrate into the essence of the Most High? "God is a Spirit," John 4:24 , and our gross conceptions are but ill-adapted to the contemplation of a pure and spiritual Being. We know not the essence of our own mind, nor the precise distinction of its several faculties; and why then should we hope to comprehend the personal characters which exist in the Godhead? "If I tell you earthly things, and you understand them not, how shall ye understand if I tell you heavenly things?" When we attempt to investigate the nature of the Deity, whose existence is commensurate with eternity, by whose power the universe was created, and by whose wisdom it is governed; whose presence fills all space, and whose knowledge extends to the thoughts of every man in every age, and to the events of all places, past, present, and to come, the mind is quickly lost in the vastness of these ideas, and, unable to find any sure guide to direct its progress, it becomes, at every step, more bewildered and entangled in the endless mazes of metaphysical abstraction. "God is a God that hideth himself." "We cannot by searching find out God." "Behold, God is great, and we know him not,"
Job 23:9; Job 11:7; Job 36:26 . "Such knowledge is too wonderful and excellent for us; it is high; we cannot attain unto it," Psalms 139:6 . It is for us, simply and in that docile spirit which becomes us, to receive the testimony of God as to himself, and to fix ourselves upon that firmest of all foundations, and most rational of all evidence, "Thus saith the Lord."
Hastings' Dictionary of the Bible 
1. The doctrine approached . It is sometimes asked why we are not given a definite statement that there are three Persons in the Godhead. One reason for the absence of any such categorical and dogmatic teaching is probably to be found in the fact that the earliest hearers of the gospel were Jews, and that any such pronouncement might (and probably would) have seemed a contradiction of their own great truth of the unity of the Godhead. Consequently, instead of giving an intellectual statement of doctrine, which might have led to theological and philosophic discussion, and ended only in more Intense opposition to Christianity, the Apostles preached Jesus of Nazareth as a personal Redeemer from sin, and urged on every one the acceptance of Him and His claims. Then, in due course, would come the inevitable process of thought and meditation upon this personal experience, and this would in turn lead to the inference that Jesus, from whom, and in whom, these experiences were being enjoyed, must be more than man, must be none other than Divine, ‘for who can forgive sins but God only?’ Through such a personal impression and inference based on experience, a distinction in the Godhead would at once be realized. Then, in the course of their Christian life, and through fuller instruction, would be added the personal knowledge and experience of the Holy Spirit, and once again a similar inference would in due course follow, making another distinction in their thought of the Godhead. The intellectual conception and expression of these distinctions probably concerned only comparatively few of the early believers, but nevertheless all of them had in their lives an experience of definite action and blessing which could only have been from above, and which no difficulty of intellectual correlation or of theological co-ordination with former teachings could invalidate and destroy.
2. The doctrine derived . The doctrine of the Trinity is an expansion of the doctrine of the Incarnation, and emerges out of the personal claim of our Lord. We believe this position can be made good from the NT. We take first the Gospels, and note that our Lord’s method of revealing Himself to His disciples was by means of personal impression and influence. His character, teaching, and claim formed the centre and core of everything, and His one object was, as it were, to stamp Himself on His disciples, knowing that in the light of fuller experience His true nature and relations would become clear to them. We see the culmination of this impression and experience in the confession of the Apostle, ‘My Lord and my God.’ Then, as we turn to the Acts of the Apostles, we find St. Peter preaching to Jews, and emphasizing two associated truths: (1) the Sonship and Messiahship of Jesus, as proved by the Resurrection, and (2) the consequent relation of the hearers to Him as to a Saviour and Master. The emphasis is laid on the personal experience of forgiveness and grace, without any attempt to state our Lord’s position in relation to God. Indeed, the references to Jesus Christ as the ‘Servant [wrongly rendered in AV [Note: Authorized Version.] ‘Son’] of God’ in Acts 3:13; Acts 3:26; Acts 4:27 , seem to show that the Christian thought regarding our Lord was still immature, so far as there was any purely Intellectual consideration of it. It is worthy of note that this phrase, which is doubtless the NT counterpart of Isaiah’s teaching on the ‘Servant of the Lord,’ is not found in the NT later than these earlier chapters of the Acts. Yet in the preaching of St. Peter the claim made for Jesus of Nazareth as the Source of healing ( Acts 3:6; Acts 3:16 ), the Prince-Leader of Life ( Acts 3:15 ), the Head Stone of the corner ( Acts 4:11 ), and the one and only Way of Salvation ( Acts 4:12 ), was an unmistakable assumption of the position and power of Godhead.
In the same way the doctrine of the Godhead of the Holy Spirit arises directly out of our Lord’s revelation. Once grant a real personal distinction between the Father and the Son, and it is easy to believe it also of the Spirit as revealed by the Son. As long as Christ was present on earth there was no room and no need for the specific work of the Holy Spirit, but as Christ was departing from the world He revealed a doctrine which clearly associated the Holy Spirit with Himself and the Father in a new and unique way ( John 14:16-17; John 14:26; John 15:26; John 16:7-15 ). Arising immediately out of this, and consonant with it, is the place given to the Holy Spirit in the Book of the Acts. From ch. 5, where lying against the Holy Spirit is equivalent to lying against God ( John 5:3-4; John 5:9 ), we see throughout the book the essential Deity of the Holy Spirit in the work attributed to Him of superintending and controlling the life of the Apostolic Church ( John 2:4 , John 8:29 , John 10:19 , John 13:2; John 13:4 , John 16:6-7 , John 20:25 ).
Then, as we pass to the Epistles, we find references to our Lord Jesus and to the Holy Spirit which imply unmistakably the functions of Godhead. In the opening salutations our Lord is associated with God as the Source of grace and peace ( 1 Thessalonians 1:1 f., 1 Peter 1:2 ), and in the closing benedictions as the Divine Source of blessing ( Romans 15:30 , 2 Thessalonians 3:16; 2 Thessalonians 3:18 ). In the doctrinal statements He is referred to in practical relation to us and to our spiritual life in terms that can be predicated of God only, and in the revelations concerning things to come He is stated to be about to occupy a position which can refer to God only. In like manner, the correlation of the Holy Spirit with the Father and the Son in matters essentially Divine is clear ( 1 Corinthians 2:4-6 , 2 Corinthians 13:14 , 1 Peter 1:2 ).
In all these assertions and implications of the Godhead of Jesus Christ, it is to be noted very carefully that St. Paul has not the faintest idea of contradicting his Jewish monotheism. Though he and others thus proclaimed the Godhead of Christ, it is of great moment to remember that Christianity was never accused of polytheism. The NT doctrine of God is essentially a form of monotheism, and stands in no relation to polytheism. There can be no doubt that, however and whenever the Trinitarian idea was formulated, it arose in immediateconnexion with the monotheism of JudÃ¦a; and the Apostles, Jews though they were, in stating so unmistakably the Godhead of Jesus Christ, are never once conscious of teaching anything inconsistent with their most cherished ideas about the unity of God.
3. The doctrine confirmed . When we have approached the doctrine by means of the personal experience of redemption, we are prepared to give full consideration to the two lines of teaching found in the NT. ( a ) One line of teaching insists on the unity of the Godhead ( 1 Corinthians 8:4 , James 2:19 ); and ( b ) the other line reveals distinctions within the Godhead ( Matthew 3:16-17; Matthew 28:19 , 2 Corinthians 13:14 ). We see clearly that (1) the Father is God ( Matthew 11:25 , Romans 15:6 , Ephesians 4:6 ); (2) the Son is God ( John 1:1; John 1:18; John 20:28 , Acts 20:26 , Romans 9:5 , Hebrews 1:8 , Colossians 2:9 , Philippians 2:6 , 2 Peter 1:1 ); (3) the Holy Spirit is God ( Acts 5:3-4 , 1 Corinthians 2:10-11 , Ephesians 2:22 ); (4) the Father, Son, and Holy Spirit are distinct from one another, sending and being sent, honouring and being honoured. The Father honours the Son, the Son honours the Father, and the Holy Spirit honours the Son ( John 15:26; John 16:13-14; John 17:1; John 17:8; John 17:18; John 17:23 ). (5) Nevertheless, whatever relations of subordination there may be between the Persons in working out redemption, the three are alike regarded as God. The doctrine of the Trinity is the correlation, co-ordination, and synthesis of the teaching of these passages. In the Unity of the Godhead there is a Trinity of Persons working out redemption. God the Father is the Creator and Ruler of man and the Provider of redemption through His love ( John 3:16 ). God the Son is the Redeemer, who became man for the purpose of our redemption. God the Holy Spirit is the ‘Executive of the Godhead,’ who applies to each believing soul the benefits of redemption. The elements of the plan of redemption thus find their root, foundation, and spring in the nature of the Godhead; and the obvious reason why these distinctions which we express by the terms ‘Person’ and ‘Trinity’ were not revealed earlier than NT times is that not until then was redemption accomplished.
4. The doctrine stated . By the Trinity, therefore, we mean the specific and unique Christian idea of the Godhead. The foundation of the Christian idea of the Godhead is that of the One Supreme Almighty Spirit whom we worship, to whom we pray, from whom we receive grace, and whom we serve. But the specific Christian thought of God is that of a Spirit, in the unity of whose being is revealed a distinction of Persons whom we call Father, Son, and Holy Spirit; the God from whom, through whom, and by whom all things come the Father as the primal Source, the Son as the redemptive Mediator, and the Holy Spirit as the personal Applier of life and grace. The Christian idea of the Trinity may be summed up in the familiar words: ‘The Father is God, the Son is God, and the Holy Ghost is God. And yet they are not three Gods, but one God. The Godhead of the Father, and of the Son, and of the Holy Ghost is all one, the Glory equal, the Majesty coeternal. And in this Trinity none is afore or after other: none is greater or less than another, but the whole three Persons are co-eternal together and co-equal.’
The term ‘Trinity’ dates from the second century, being found in Greek in Theophilus of Antioch (a.d. 181); and the actual Latin word, from which we derive our English term, in Tertullian (a.d. 200). Its use is sometimes criticised because it is not found in the Bible, but this is no valid objection to it. Like other words. e.g . ‘Incarnation,’ it expresses in technical language the truth about the Godhead which is found implicitly in the NT. The real question is whether it is true, and whether it is fairly expressive of the Bible truth. It is intended to express and safeguard that real and essential unity of the Godhead which is at the root of the distinctions of Father, Son, and Holy Spirit. The term ‘Person’ is also sometimes objected to. Like all human language, it is liable to be accused of inadequacy and even positive error. It certainly must not be pressed too far, or it will lead to Tritheism. While we use the term to denote distinctions in the Godhead, we do not imply distinctions which amount to separateness, but distinctions which are associated with essential mutual coinherence or inclusiveness. We intend by the term ‘Person’ to express those real distinctions of Father, Son, and Holy Spirit which are found amid the oneness of the Godhead, distinctions which are no mere temporary manifestations of Deity, but essential and permanent elements within the Divine unity.
5. The doctrine supported . When all this is granted and so far settled, we may find a second line of teaching to support the foregoing in the revelation of God as Love. Following the suggestion of St. Augustine, most modern theologians have rightly seen in this a safe ground for our belief. It transcends, and perhaps renders unnecessary, all arguments drawn from human and natural analogies of the doctrine. ‘God is love’ means, as some one has well said, ‘God as the Infinite home of all moral emotions, the fullest and most highly differentiated life.’ Love must imply relationships, and, as He is eternally perfect in Himself, He can realize Himself as Love only through relationships within His own Being. We may go so far as to say that this is the only way of obtaining a living thought about God. Belief in Theism postulates a self-existent God, and yet it is impossible to think of a God without relationships. These relationships must be eternal and prior to His temporal relationships to the universe of His own creation. He must have relationships eternally adequate, and worthy, and when once we realize that love must have an object in God as well as in ourselves, we have the germ of that distinction in the Godhead which is theologically known as the Trinity.
6. The doctrine anticipated . At this stage, and only here, we may seek another support for the doctrine. In the light of the facts of the NT we cannot refrain from asking whether there may not have been some adumbrations of it in the OT. As the doctrine arises directly out of the facts of the NT, we do not for an instant look for any full discovery of it in the OT. But if the doctrine be true, we might expect that Christian Jews, at any rate, would seek for some anticipation of it in the OT. We believe we find it there. ( a ) The references to the ‘ Angel of Jehovah ’ prepare the way for the Christian doctrine of a distinction in the Godhead ( Genesis 18:2; Genesis 18:16; Genesis 17:22 with Genesis 19:1 , Joshua 5:13-15 with Joshua 6:1 , Judges 13:8-21 , Zechariah 13:7 ). ( b ) Allusions to the ‘ Spirit of Jehovah ’ form another line of OT teaching. In Genesis 1:2 the Spirit is an energy only, but in subsequent books an agent ( Isaiah 40:13; Isaiah 48:16; Isaiah 59:19; Isaiah 63:10 f.). ( c ) The personification of Divine Wisdom is also to be observed, for the connexion between the personification of Wisdom in Proverbs 8:1-36 , the Logos of John 1:1-18 , and the ‘wisdom’ of 1 Corinthians 1:24 can hardly be accidental. ( d ) There are also other hints, such as the triplicity of the Divine Names ( Numbers 6:24-27 , Psalms 29:3-5 , Isaiah 6:3 ), which may not be pressed, but can hardly be overlooked. Hints are all that were to be expected or desired until the fulness of time should have come. The function of Israel was to guard God’s transcendence and omnipresence; it was for Christianity to develop the doctrine of the Godhead into the fulness, depth, and richness that we find in the revelation of the Incarnate Son of God.
7. The doctrine justified . ( a ) From the facts of Scripture . It emerges clearly from the claim of Christ; it is an extension of the doctrine of the Incarnation. If the Incarnation was real, the Trinity is true. ( b ) From the facts of Christian experience . It is a simple fact that Christians of all periods of history claim to have personal direct fellowship with Christ. This claim must be accounted for. It is possible only by predicating Deity of our Lord, for such fellowship would be impossible with one who is not God. ( c ) From the facts of history . Compared with other religions, Christianity makes God a reality in a way in which no other system does. The doctrine of the Trinity has several positive theological and philosophical advantages over the Unitarian conception of God, but especially is this so in reference to the relation of God to the world. There are two conceivable relations of God to the world as transcendent (in Mohammedanism), or as immanent (in Buddhism). The first alone means Deism, the second alone Pantheism. But the Christian idea is of God as at once transcendent and immanent. It is therefore the true protection of a living Theism, which otherwise oscillates uncertainly between these two extremes of Deism and Pantheism, either of which is false to It. It is only in Christianity that the Semitic and Aryan conceptions of God are united, blended, correlated, balanced, and preserved. ( d ) From reason . It is simple truth to say that, if Jesus be not God, Christians are idolaters, for they worship One who is not God. There is no other alternative. But when once the truth of the doctrine of the Trinity is regarded as arising out of Christ’s claim to Godhead as Divine Redeemer, reason soon finds its warrant for the doctrine. The doctrine of the Trinity comes to us by revelation and not by nature, though it is soon seen to have points of contact with thought and reason.
The doctrine ‘started in the concrete, with the baptismal formula â€¦ emanating from Jesus Christ. And throughout the history of its dogmatic formulation, we are confronted with this fact. It was regarded as a revelation by the men who shaped its intellectual expression; and it was only in the process â€¦ of that expression that its congruity with human psychology came out; that psychology in fact being distinctly developed in the effort to give it utterance.â€¦ They did not accommodate Christian religion to their philosophy, but philosophy to their Christian religion.’ This doctrine appealed ‘first to unsophisticated men, far removed from Alexandria or Athens; yet the very words in which it does so, turn out, upon analysis, to involve a view of personality which the world had not attained, but which, once stated, is seen to be profoundly, philosophically true’ (Illingworth, Personality , p. 212f.).
W. H. Griffith Thomas.
Bridgeway Bible Dictionary 
God is one, but he exists as a Trinity. Any attempt to define the Trinity is difficult and dangerous, as it is an attempt to do what the Bible does not do. However, by a study of the biblical teaching about God, we understand that although God is one, the form in which his godhead exists is that of three persons – Father, Son and Holy Spirit. Each of the three persons is fully God, yet there is only one God, not three.
One God, three persons
The Old Testament gives little clear teaching about the Trinity, for the emphasis there is on the oneness of God. Israel lived among nations that had many gods. The important truth impressed upon Israel was that there is only one God, and he is a unity ( Deuteronomy 6:4).
Our understanding of the Trinity comes largely from the New Testament. This does not mean that the God of Old Testament times differed from the God of New Testament times, or that a God who was previously ‘one’ branched out into three. God has always existed in a Trinity. What is new in the New Testament is the revelation of the Trinity, not the Trinity itself.
The reason why the revelation of the Trinity is new in the New Testament is that it was related to the great acts of God in bringing his plan of salvation to completion in Christ. God did not reveal his truth in the form of abstract truths unrelated to the situation in which the people of the time lived. Rather he revealed his truth step by step as he brought his people closer to the full salvation he had planned.
Nevertheless, with the fuller knowledge that Christians gain from the New Testament, they may see suggestions of the Trinity in the Old Testament. Such suggestions are there, even though believers of Old Testament times may not have seen them (cf. 1 Peter 1:10-12).
For example, in the Old Testament references to the creation there was an inseparable connection between God, the creative power of God’s Word, and the life-giving power of God’s Spirit ( Genesis 1:1-3; Job 33:4; Psalms 33:6). But with the coming of Jesus, people gained a clearer understanding of the work of the Trinity in all the activity of God, including the creation ( John 1:1-4). This understanding increased further as Jesus taught his followers and left with them the gift of the Holy Spirit, who would interpret his teaching and continue to enlighten them ( John 16:13-15).
The revelation through Jesus Christ
When God took human form in the person of Jesus Christ, much that was previously secret and hidden became open. Jesus revealed God to the world ( John 1:1; John 1:14; John 1:18).
Through Jesus Christ, God was now physically present in the world. But in another sense he was not physically present. Jesus made it plain that when people saw him they saw God ( John 8:58-59), but he also made it plain that God existed elsewhere; for he himself came from God, and during his earthly life he spoke to God ( John 6:38; John 11:41-42).
Jesus explained this apparent contradiction by pointing out that he was God the Son, and that the one from whom he came and to whom he spoke was God the Father. Although these two persons were distinct, they were uniquely united ( John 5:18; John 5:37; John 8:42; John 10:30; John 11:41; John 14:9; John 16:26-28; see Father; Son Of God )
Having become a human being, God the Son now gave the additional revelation that there was a third person in the Godhead, the Holy Spirit. All three persons were involved in the miraculous coming of the Son into the world ( Luke 1:35), and the life and ministry of Jesus that followed should have shown people that God existed as a Trinity – Father, Son and Holy Spirit ( Matthew 3:16-17; Matthew 12:28; Luke 4:18; John 3:34-35). Just before he completed his ministry, Jesus explained about the Holy Spirit more fully. He promised that after he returned to his Father, he and the Father would send the Holy Spirit to be with his disciples, as he himself had been previously ( John 14:16-17; John 14:26; John 15:26).
The Holy Spirit, though a separate person from the Father and the Son, is inseparably united with both ( Acts 2:32-33). He comes from the Father as the bearer of the Father’s power and presence ( John 15:26; John 16:7-11), and he comes from the Son as the bearer of the Son’s power and presence ( John 14:18; John 16:7; Romans 8:9; see Holy Spirit ). Although there is a distinction between the three persons of the Godhead, there is no division. Each has his own personality and will, but he never acts independently of the others ( John 14:26; Acts 16:6-7; Galatians 4:6).
No change in God
This three-in-one and one-in-three unity of the Godhead is well illustrated in the command that Jesus gave to his disciples to baptize their converts ‘in the name of the Father and of the Son and of the Holy Spirit’ ( Matthew 28:19). In Jewish thought the name represented the person (see Name ). Jesus here spoke of the name (singular), indicating one God, but at the same time he showed that this God existed in three persons. And these three persons were distinct from each other, yet uniquely and inseparably united.
As a God-fearing Jew, Jesus gave his complete allegiance to the one and only true God, and he taught others to do likewise ( Deuteronomy 6:4; Matthew 22:37). Jesus’ statement therefore indicated that this God whom Israelites of former times worshipped under the name of Yahweh (Jehovah) was the same God as Christians worshipped under the name of Father, Son and Holy Spirit. The God who is ‘one’ is at the same time a Trinity.
Faith of the New Testament writers
The early disciples reached a fuller understanding of the Trinity through the life, teaching, death and triumph of Jesus Christ. They then passed on their insights through the writings of the New Testament. They never tried to define the Trinity, nor did they try to ‘prove’ it in a theoretical sense. Since they knew God as the one who gave his Son to die for them and gave his Spirit to indwell them, they thought of God in no other way than as a Trinity. The New Testament writings therefore assume the fact of the Trinity at all times ( Ephesians 4:4-6; Ephesians 5:18-20; 1 Thessalonians 1:3-5; 1 Peter 1:2). Yet they also assume the oneness of God ( Romans 3:30; 1 Corinthians 8:4).
In keeping with the teachings of Jesus, the teachings of the New Testament writers show that the three persons of the Trinity are fully and equally God. No one person is inferior to, or superior to, any other. Concerning their operations, however, there is a difference. The Son is willingly subject to the Father ( John 5:30; John 7:16; John 12:49; Philippians 2:5-8; Hebrews 10:5-7), and the Spirit is willingly subject to both the Father and the Son ( John 14:26; John 15:26; John 16:13-15; Romans 8:26-27; Galatians 4:6; Philippians 1:19).
Because of the unity between the persons of the Trinity, all three are active in all the work of God. This work is not, as it were, divided among three persons. In a sense, what one does they all do. But the Bible story shows that there is also a sense in which their activities differ.
The name ‘Father’ speaks of one who has to do with the origin of things, and this is seen in the great works of creation, history and redemption ( Malachi 2:10; Ephesians 1:3-10; Hebrews 12:9; James 1:17). The Son is the one who reveals the Father, the one through whom the Father does these works ( John 10:25; John 10:38; John 14:10; 2 Corinthians 5:19; Ephesians 1:3-10; Colossians 1:15-16). The Spirit is the one by whom God’s power operates in the world, the one who applies the truth of God’s works to people’s lives ( John 14:17; John 16:7-13; Acts 1:8; Romans 8:2-4; Galatians 5:16-18; 1 Peter 1:2). God’s salvation comes from the Father, through the Son, by the Spirit ( Titus 3:4-6), and people’s approach to God is by the Spirit, through the Son, to the Father ( Ephesians 2:18).
Relationship with the triune God
In making statements about the Father, the Son and the Holy Spirit, the New Testament writers were not attempting a theoretical analysis of God. Their concern was not to set out in systematic form the character and activities of the persons of the Trinity, but to express the relationship that Christians have with God. Christians cannot fully understand the mysteries of the Godhead, but they should try to learn all they can about God; for the life they have in Christ depends on God being the sort of God he is – a Trinity.
Jesus Christ, for example, could not be humankind’s Saviour if he were not the unique person that he is. The fact of the Trinity was essential to his birth ( Luke 1:35), his life ( John 3:34; John 5:36-37; Hebrews 2:3-4; 1 John 5:6-9), his death ( Romans 8:32; Galatians 2:20; Hebrews 9:14), his resurrection ( Acts 2:42; John 10:18; Romans 8:11) and his exaltation ( Acts 5:30-32).
The fact of the Trinity is essential also for the life of believers: their indwelling by God ( Ephesians 4:6; Colossians 1:27; 1 Corinthians 6:19); their sanctification ( John 17:17; Hebrews 2:11; 1 Corinthians 6:11), their enjoyment of salvation ( 2 Corinthians 13:14), their exercise of prayer ( Romans 8:26-27; Romans 8:34; Ephesians 2:18), their eternal security ( John 10:28-29; Ephesians 4:30) and their ultimate victory over death ( John 5:21; Romans 8:11).
Likewise the Trinity is involved in the life of the church ( 1 Corinthians 12:4-6) and in Christian service ( 2 Corinthians 3:5-6; 1 Timothy 1:12; Acts 20:28). The Scriptures that Christians possess are a provision from the triune God ( 2 Timothy 3:16-17; 1 Peter 1:10-11; 2 Peter 1:21). They are one of the means by which the same God wants to work in and through his people, as they build themselves up in their faith and prepare themselves for fellowship with him in the age to come ( Judges 1:20-21).
Holman Bible Dictionary 
A proper biblical view of the Trinity balances the concepts of unity and distinctiveness. Two errors that appear in the history of the consideration of the doctrine are tritheism and unitarianism. In tritheism, error is made in emphasizing the distinctiveness of the Godhead to the point that the Trinity is seen as three separate Gods, or a Christian polytheism. On the other hand, unitarianism excludes the concept of distinctiveness while focusing solely on the aspect of God the Father. In this way, Christ and the Holy Spirit are placed in lower categories and made less than divine. Both errors compromise the effectiveness and contribution of the activity of God in redemptive history.
The biblical concept of the Trinity developed through progressive revelation. See Revelation. The Old Testament consistently affirms the unity of God through such statements as, “Hear, O Israel: the Lord our God is one Lord” ( Deuteronomy 6:4 ). See Shema . God's oneness is stressed to caution the Israelites against the polytheism and practical atheism of their heathen neighbors.
The Old Testament does feature implications of the trinitarian idea. This does not mean that the Trinity was fully knowable from the Old Testament, but that a vocabulary was established through the events of God's nearness and creativity; both receive developed meaning from New Testament writers. For example, the word of God is recognized as the agent of creation ( Psalm 33:6 ,Psalms 33:6, 33:9; compare Proverbs 3:19; Proverbs 8:27 ), revelation, and salvation ( Psalm 107:20 ). This same vocabulary is given distinct personality in John's prologue ( John 1:1-4 ) in the person of Jesus Christ. Other vocabulary categories include the wisdom of God ( Proverbs 8:1 ) and the Spirit of God ( Genesis 1:2; Psalm 104:30; Zechariah 4:6 ).
A distinguishing feature of the New Testament is the doctrine of the Trinity. It is remarkable that New Testament writers present the doctrine in such a manner that it does not violate the Old Testament concept of the oneness of God. In fact, they unanimously affirm the Hebrew monothestic faith, but they extend it to include the coming of Jesus and the outpouring of the Holy Spirit. The early Christian church experienced the God of Abraham in a new and dramatic way without abandoning the oneness of God that permeates the Old Testament. As a fresh expression of God, the concept of the Trinity—rooted in the God of the past and consistent with the God of the past—absorbs the idea of the God of the past, but goes beyond the God of the past in a more personal encounter.
The New Testament does not present a systematic presentation of the Trinity. The scattered segments from various writers that appear throughout the New Testament reflect a seemingly accepted understanding that exists without a full-length discussion. It is embedded in the framework of the Christian experience and simply assumed as true. The New Testament writers focus on statements drawn from the obvious existence of the trinitarian experience as opposed to a detailed exposition.
The New Testament evidence for the Trinity can be grouped into four types of passages. The first is the trinitarian formula of Matthew 28:19; 2 Corinthians 13:14; 1 Peter 1:2; Revelation 1:4 . In each passage a trinitarian formula, repeated in summation fashion, registers a distinctive contribution of each person of the Godhead. Matthew 28:19 , for example, follows the triple formula of Father, Son, and Holy Spirit that distinguishes Christian baptism. The risen Lord commissioned the disciples to baptize converts with a trinitarian emphasis that carries the distinctiveness of each person of the Godhead while associating their inner relationship. This passage is the clearest scriptural reference to a systematic presentation of the doctrine of the Trinity.
Paul, in 2 Corinthians 13:14 , finalized his thoughts to the Corinthian church with a pastoral appeal that is grounded in “the grace of the Lord Jesus Christ, and the love of God, and the fellowship of the Holy Spirit” (NIV). The formulation is designed to have the practical impact of bringing that divided church together through their personal experinece of the Trinity in their daily lives. Significantly, in the trinitarian order Christ is mentioned first. This reflects the actual process of Christian salvation, since Christ is the key to opening insight into the work of the Godhead. Paul was calling attention to the trinitarian consciousness, not in the initial work of salvation which has already been accomplished at Corinth, but in the sustaining work that enables divisive Christians to achieve unity.
In 1 Peter 1:2 , the trinitarian formula is followed with reference to each person of the Godhead. The scattered Christians are reminded through reference to the Trinity that their election (foreknowledge of the Father) and redemption (the sanctifying work of the Spirit) should lead to holy living obedience to the Son).
John addressed the readers of Revelation with an expanded trinitarian formula that includes references to the persons of the Godhead ( Revelation 1:4-6 ). The focus on the triumph of Christianity crystallizes the trinitarian greeting into a doxology that acknowledges the accomplished work and the future return of Christ. This elongated presentation serves as an encouragement to churches facing persecution.
A second type of New Testament passage is the triadic form. Two passages cast in this structure are Ephesians 4:4-6 and 1 Corinthians 12:3-6 . Both passages refer to the three Persons, but not in the definitive formula of the previous passage. Each Scripture balances the unity of the church. Emphasis is placed on the administration of gifts by the Godhead.
A third category of passages mentions the three persons of the Godhead, but without a clear triadic structure. In the accounts of the baptism of Jesus ( Matthew 3:3-17; Mark 1:9-11; and Luke 3:21-22 ), the three synoptic writers recorded the presence of the Trinity when the Son was baptized, the Spirit descended, and the Father spoke with approval. Paul, in Galatians 4:4-6 , outlined the work of the Trinity in the aspect of the sending Father. Other representative passages in this category ( 2 Thessalonians 2:13-15; Titus 3:4-6; and Jude 1:20-21 ) portray each member of the Trinity in relation to a particular redemptive function.
The fourth category of trinitarian passages includes those presented in the farewell discourse of Jesus to His disciples ( John 14:16; John 15:26; John 16:13-15 ). In the context of these passages, Jesus expounded the work and ministry of the third person of the Godhead as the Agent of God in the continuing ministry of the Son. The Spirit is a Teacher who facilitates understanding on the disciples' part and, in being sent from the Father and the Son, is one in nature with the other Persons of the Trinity. He makes known the Son and “at the same time makes known the Father who is revealed in the Son” ( John 16:15 ). The discourse emphasizes the interrelatedness of the Trinity in equality and operational significance.
All of these passages are embryonic efforts by the early church to express its awareness of the Trinity. The New Testament is Christological in its approach, but it involves the fullness of God being made available to the individual believer through Jesus and by the Spirit. The consistent trinitarian expression is not a formulation of the doctrine, as such, but reveals an experiencing of God's persistent self-revelation.
In the postbiblical era, the Christian church tried to express its doctrine in terms that were philosophically acceptable and logically coherent. Greek categories of understanding began to appear in explanation efforts. Discussion shifted from the New Testament emphasis on the function of the Trinity in redemptive history to an analysis of the unity of essence of the Godhead.
A major question during those early centuries focused on the oneness of God. The Sabelians described the Godhead in terms of modes that existed only one at a time. This theory upheld the unity of God, but excluded His permanent distinctiveness. The Docetists understood Christ as an appearance of God in human form, while Ebonites described Jesus as an ordinary man indwelt with God's power at baptism. Arius was also an influential theologian who viewed Jesus as subordinate to God. To Arius, Jesus was a being created by God, higher than man, but less than God. This idea, as well as the others, was challenged by Athanasius at Nicea (A.D. 325), and the council decided for the position of Jesus as “of the exact same substance as the Father.”
Probably the most outstanding thinker of the early centuries was Augustine of Hippo (A.D. 354-430). He began with the idea of God as one substance and sought explanation of the Godhead in psychological analogy: a person exists as one being with three dimensions of memory, understanding, and will; so also the Godhead exists as a unity of Father, Son, and Holy Spirit. While this explanation is helpful and contains the concept of three persons in one, it does not resolve the complex nature of God.
Perhaps four statements can summarize and clarify this study.
1. God is One. The God of the Old Testament is the same God of the New Testament. His offer of salvation in the Old Testament receives a fuller revelation in the New Testament in a way that is not different, but more complete. The doctrine of the Trinity does not abandon the monotheistic faith of Israel.
2. God has three distinct ways of being in the redemptive event, yet He remains an undivided unity. That God the Father imparts Himself to mankind through Son and Spirit without ceasing to be Himself is at the very heart of the Christian faith. A compromise in either the absolute sameness of the Godhead or the true diversity reduces the reality of salvation.
3. The primary way of grasping the concept of the Trinity is through the threefold participation in salvation. The approach of the New Testament is not to discuss the essence of the Godhead, but the particular aspects of the revelatory event that includes the definitive presence of the Father in the person of Jesus Christ through the Holy Spirit.
4. The doctrine of the Trinity is an absolute mystery. It is primarily known, not through speculation, but through experiencing the act of grace through personal faith. See God; Jesus Christ; Holy Spirit .
Jerry M. Henry
Charles Buck Theological Dictionary 
The union of three in one; generally applied to the ineffable mystery of three persons in one God,
Father, Son, and Holy Spirit. This doctrine is rejected by many because it is incomprehensible; but, as Mr. Scott observes, if distinct personality, agency, and divine perfections, be in Scripture ascribed to the Father, and to the Son, and to the Holy Spirit, no words can more exactly express the doctrine, which must unavoidably be thence inferred, than those commonly used on this subject, viz. that there are three distinct Persons in the Unity of the Godhead. The sacred oracles most assuredly teach us, that the One living and true God is, in some inexplicable manner, Triune, for he is spoken of, as One in some respects, and as Three in others, Genesis 1:26 , Genesis 2:6-7 . Is. 48: 16. Is. 34: 16. 2 Corinthians 13:14 . John 14:23 . Matthew 28:19 . 2 Thessalonians 3:3 . 1 John 5:7 . Acts 5:3-4 . The Trinity of Persons in the Diety consists with the Unity of the Divine Essence; though we pretend not to explain the modus of it, and deem those reprehensible who have attempted it; as the modus in which any being subsists, according to its distinct nature and known properties, is a secret to the most learned naturalists to this present day, and probably will always continue so. But if the most common of God's works, with which we are the most conversant, be in this respect incomprehensible, how can men think that the modus existetendi (or manner of existence) of the infinite Creator can be level to their capacities?
The doctrine of the Trinity is indeed a mystery, but no man hath yet shown that it involves in it a real contradiction. Many have ventured to say, that it ought to be ranked with transubstantiation, as equally absurd. But Archbishop Tillotson has shown, by the most convincing arguments imaginable, that transubstantiation includes, the most palpable contradictions; and that we have the evidence of our eyes, feeling, and taste, that what we receive in the Lord's supper is bread, and not the body of a man; whereas we have the testimony of our eyes alone, that the words "This is my body, " are at all in the Scriptures. Now this in intelligible to the meanest capacity: it is fairly made out, and perfectly unanswerable: but who ever attempted thus to prove the doctrine of the Trinity to be self-contradictory? What testimony of our senses, or what demonstrated truth, does it contradict? Yet till this be shown, it is neither fair nor convincing, to exclaim against it as contradictory, absurd, and irrational."
See articles Jesus Christ and Holy Ghost; also Owen, Watts, Jones, S. Browne, Fawcett, A. Taylor, J. Scott, Sampson, and Wesley's Pieces on the Subject; Bull's Defensio Fidei Nicaenae; Dr. Allix's Testimonies of the Jewish Church; Display of the Trinity by a Layman; Scott's Essays.
Morrish Bible Dictionary 
A word only used to convey the thought of a plurality of Persons in the Godhead. This was revealed at the baptism of the Lord Jesus. The Holy Spirit descended 'like a dove' and abode upon Him; and God the Father declared "This is my beloved Son in whom I am well pleased." That the Father is a distinct Person and is God is plainly stated, as in John 20:17 . Many passages prove that the Lord Jesus is God: one will suffice: ". . . . in his Son Jesus Christ. This is the true God, and eternal life." 1 John 5:20 . That the Holy Spirit is a Person and is God the following passages clearly prove: Genesis 1:2; Matthew 4:1; John 16:13; Acts 10:19; Acts 13:2,4; Acts 20:28; Romans 15:30; 1 Corinthians 2:10 . The three Persons are also named in the formula instituted by Christ in baptism. Matthew 28:19 . Yet there is but one God. 1 Timothy 2:5 . Satan will have an imitation of the Trinity in the Roman beast, the false prophet, and himself. Revelation 13:4,11; Revelation 20:10 .
People's Dictionary of the Bible 
Trinity. This word does not occur in Scripture. As a fact the Scripture reveals the doctrine of the Trinity in two ways: first in passages in which the Father, Son, and Holy Spirit are mentioned together as God; and secondly, in passages which speak of each as divine. In the New Testament clear evidence is given. See Matthew 3:16-17; Matthew 28:19; 1 Corinthians 12:3-6; 2 Corinthians 13:14; Ephesians 4:4-6; Titus 3:4-6; 1 Peter 1:2; Judges 1:20-21. These passages, carefully read, are sufficient to prove that "the Godhead of the Father, of the Son, and of the Holy Ghost is one, the glory equal, the majesty co-eternal; such as the Father is, such is the Son, and such is the Holy Ghost; the Father is God, the Son is God, and the Holy Ghost is God; and yet they are not three Gods, but one God."
Webster's Dictionary 
(1): ( n.) Any union of three in one; three units treated as one; a triad, as the Hindu trinity, or Trimurti.
(2): ( n.) Any symbol of the Trinity employed in Christian art, especially the triangle.
(3): ( n.) The union of three persons (the Father, the Son, and the Holy Ghost) in one Godhead, so that all the three are one God as to substance, but three persons as to individuality.
Easton's Bible Dictionary 
Deuteronomy 6:4 1 Kings 8:60 Isaiah 44:6 Mark 12:29,32 John 10:30 2
Hastings' Dictionary of the New Testament 
International Standard Bible Encyclopedia 
trin´i - ti
1. The Term "Trinity"
3. No Rational Proof of It
4. Finds Support in Reason
5. Not Clearly Revealed in the Old Testament
6. Prepared for in the Old Testament
7. Presupposed Rather Than Inculcated in the New Testament
8. Revealed in Manifestation of Son and Spirit
9. Implied in the Whole New Testament
10. Conditions the Whole Teaching of Jesus
11. Father and Son in Johannine Discourses
12. Spirit in Johannine Discourses
13. The Baptismal Formula
14. Genuineness of Baptismal Formula
15. Paul's Trinitarianism
16. Conjunction of the Three in Paul
17. Trinitarianism of Other New Testament Writers
18. Variations in Nomenclature
19. Implications of "Son" and "Spirit"
20. The Question of Subordination
22. Formulation of the Doctrine
1. The Term "Trinity":
The term "Trinity" is not a Biblical term, and we are not using Biblical language when we define what is expressed by it as the doctrine that there is one only and true God, but in the unity of the Godhead there are three coeternal and coequal Persons, the same in substance but distinct in subsistence. A doctrine so defined can be spoken of as a Biblical doctrine only on the principle that the sense of Scripture is Scripture. And the definition of a Biblical doctrine in such un-Biblical language can be justified only on the principle that it is better to preserve the truth of Scripture than the words of Scripture. The doctrine of the Trinity lies in Scripture in solution; when it is crystallized from its solvent it does not cease to be Scriptural, but only comes into clearer view. Or, to speak without figure, the doctrine of the Trinity is given to us in Scripture, not in formulated definition, but in fragmentary allusions; when we assemble the disjecta membra into their organic unity, we are not passing from Scripture, but entering more thoroughly into the meaning of Scripture. We may state the doctrine in technical terms, supplied by philosophical reflection; but the doctrine stated is a genuinely Scriptural doctrine.
2. Purely a Revealed Doctrine:
In point of fact, the doctrine of the Trinity is purely a revealed doctrine. That is to say, it embodies a truth which has never been discovered, and is indiscoverable, by natural reason. With all his searching, man has not been able to find out for himself the deepest things of God. Accordingly, ethnic thought has never attained a Trinitarian conception of God, nor does any ethnic religion present in its representations of the divine being any analogy to the doctrine of the Trinity.
Triads of divinities, no doubt, occur in nearly all polytheistic religions, formed under very various influences. Sometimes, as in the Egyptian triad of Osiris. Isis and Horus, it is the analogy of the human family with its father, mother and son which lies at their basis. Sometimes they are the effect of mere syncretism, three deities worshipped in different localities being brought together in the common worship of all. Sometimes, as in the Hindu triad of Brahma, Vishnu and Shiva, they represent the cyclic movement of a pantheistic evolution, and symbolize the three stages of Being, Becoming and Dissolution. Sometimes they are the result apparently of nothing more than an odd human tendency to think in threes, which has given the number three widespread standing as a sacred number (so H. Usener). It is no more than was to be anticipated, that one or another of these triads should now and again be pointed to as the replica (or even the original) of the Christian doctrine of the Trinity. Gladstone found the Trinity in the Homeric mythology, the trident of Poseidon being its symbol. Hegel very naturally found it in the Hindu Trimurti, which indeed is very like his pantheizing notion of what the Trinity is. Others have perceived it in the Buddhist Triratna (Soderblom); or (despite their crass dualism) in some speculations of Parseeism; or, more frequently, in the notional triad of Platonism (e.g. Knapp); while Jules Martin is quite sure that it is present in Philo's neo-Stoical doctrine of the "powers," especially when applied to the explanation of Abraham's three visitors. Of late years, eyes have been turned rather to Babylonia; and H. Zimmern finds a possible forerunner of the Trinity in a Father, Son, and Intercessor, which he discovers in its mythology. It should be needless to say that none of these triads has the slightest resemblance to the Christian doctrine of the Trinity. The Christian doctrine of the Trinity embodies much more than the notion of "threeness," and beyond their "threeness" these triads have nothing in common with it.
3. No Rational Proof of It:
As the doctrine of the Trinity is indiscoverable by reason, so it is incapable of proof from reason. There are no analogies to it in Nature, not even in the spiritual nature of man, who is made in the image of God. In His trinitarian mode of being, God is unique; and, as there is nothing in the universe like Him in this respect, so there is nothing which can help us to comprehend Him. Many attempts have, nevertheless, been made to construct a rational proof of the Trinity of the God head. Among these there are two which are particularly attractive, and have therefore been put forward again and again by speculative thinkers through all the Christian ages. These are derived from the implications, in the one case, of self-consciousness; in the other, of love. Both self-consciousness and love, it is said, demand for their very existence an object over against which the self stands as subject. If we conceive of God as self-conscious and loving, therefore, we cannot help conceiving of Him as embracing in His unity some form of plurality. From this general position both arguments have been elaborated, however, by various thinkers in very varied forms.
The former of them, for example, is developed by a great 17th-century theologian - B artholomew Keckermann (1614) - as follows: God is self-conscious thought; and God's thought must have a perfect object, existing eternally before it; this object to be perfect must be itself God; and as God is one, this object which is God must be the God that is one. It is essentially the same argument which is popularized in a famous paragraph (section 73) of Lessing's The Education of the Human Race . Must not God have an absolutely perfect representation of Himself - that is, a representation in which everything that is in Him is found? And would everything that is in God be found in this representation if His necessary reality were not found in it? If everything, everything without exception, that is in God is to be found in this representation, it cannot, therefore, remain a mere empty image, but must be an actual duplication of God. It is obvious that arguments like this prove too much. If God's representation of Himself, to be perfect, must possess the same kind of reality that He Himself possesses, it does not seem easy to deny that His representations of everything else must possess objective reality. And this would be as much as to say that the eternal objective coexistence of all that God can conceive is given in the very idea of God; and that is open pantheism. The logical flaw lies in including in the perfection of a representation qualities which are not proper to representations, however perfect. A perfect representation must, of course, have all the reality proper to a representation; but objective reality is so little proper to a representation that a representation acquiring it would cease to be a representation. This fatal flaw is not transcended, but only covered up, when the argument is compressed, as it is in most of its modern presentations, in effect to the mere assertion that the condition of self-consciousness is a real distinction between the thinking subject and the thought object, which, in God's case, would be between the subject ego and the object ego. Why, however, we should deny to God the power of self-contemplation enjoyed by every finite spirit, save at the cost of the distinct hypostatizing of the contemplant and the contemplated self, it is hard to understand. Nor is it always clear that what we get is a distinct hypostatization rather than a distinct substantializing of the contemplant and contemplated ego: not two persons in the Godhead so much as two Gods. The discovery of the third hypostasis - the Holy Spirit - remains meanwhile, to all these attempts rationally to construct a Trinity in the Divine Being, a standing puzzle which finds only a very artificial solution.
The case is much the same with the argument derived from the nature of love. Our sympathies go out to that old Valentinian writer - possibly it was Valentinus himself - who reasoned - perhaps he was the first so to reason - that "God is all love," "but love is not love unless there be an object of love." And they go out more richly still to Augustine, when, seeking a basis, not for a theory of emanations, but for the doctrine of the Trinity, he analyzes this love which God is into the triple implication of "the lover," "the loved" and "the love itself," and sees in this trinary of love an analogue of the Triune God. It requires, however, only that the argument thus broadly suggested should be developed into its details for its artificiality to become apparent. Richard of Victor works it out as follows: It belongs to the nature of amor that it should turn to another as caritas . This other, in God's case, cannot be the world; since such love of the world would be inordinate. It can only be a person; and a person who is God's equal in eternity, power and wisdom. Since, however, there cannot be two divine substances, these two divine persons must form one and the same substance. The best love cannot, however, confine itself to these two persons; it must become condilectio by the desire that a third should be equally loved as they love one another. Thus love, when perfectly conceived, leads necessarily to the Trinity, and since God is all He can be, this Trinity must be real. Modern writers (Sartorius, Schoberlein, J. Muller, Liebner, most lately R. H. Grutzmacher) do not seem to have essentially improved upon such a statement as this. And after all is said, it does not appear clear that God's own all-perfect Being could not supply a satisfying object of His all-perfect love. To say that in its very nature love is self-communicative, and therefore implies an object other than self, seems an abuse of figurative language.
Perhaps the ontological proof of the Trinity is nowhere more attractively put than by Jonathan Edwards. The peculiarity of his presentation of it lies in an attempt to add plausibility to it by a doctrine of the nature of spiritual ideas or ideas of spiritual things, such as thought, love, fear, in general. Ideas of such things, he urges, are just repetitions of them, so that he who has an idea of any act of love, fear, anger or any other act or motion of the mind, simply so far repeats the motion in question; and if the idea be perfect and complete, the original motion of the mind is absolutely reduplicated. Edwards presses this so far that he is ready to contend that if a man could have an absolutely perfect idea of all that was in his mind at any past moment, he would really, to all intents and purposes, be over again what he was at that moment. And if he could perfectly contemplate all that is in his mind at any given moment, as it is and at the same time that it is there in its first and direct existence, he would really be two at that time, he would be twice at once: "The idea he has of himself would be himself again." This now is the case with the Divine Being. "God's idea of Himself is absolutely perfect, and therefore is an express and perfect image of Him, exactly like Him in every respect.... But that which is the express, perfect image of God and in every respect like HIm is God, to all intents and purposes, because there is nothing wanting: there is nothing in the Deity that renders it the Deity but what has something exactly answering to it in this image, which will therefore also render that the Deity." The Second Person of the Trinity being thus attained, the argument advances. "The Godhead being thus begotten of God's loving (having?) an idea of Himself and showing forth in a distinct Subsistence or Person in that idea, there proceeds a most pure act, and an infinitely holy and sacred energy arises between the Father and the Son in mutually loving and delighting in each other.... The Deity becomes all act, the divine essence itself flows out and is as it were breathed forth in love and joy. So that the Godhead therein stands forth in yet another manner of Subsistence, and there proceeds the Third Person in the Trinity, the Holy Spirit, namely, the Deity in act, for there is no other act but the act of the will." The inconclusiveness of the reasoning lies on the surface. The mind does not consist in its states, and the repetition of its states would not, therefore, duplicate or triplicate it. If it did, we should have a plurality of Beings, not of Persons in one Being. Neither God's perfect idea of Himself nor His perfect love of Himself reproduces Himself. He differs from His idea and His love of Himself precisely by that which distinguishes His Being from His acts. When it is said, then, that there is nothing in the Deity which renders it the Deity but what has something answering to it in its image of itself, it is enough to respond - except the Deity itself. What is wanting to the image to make it a second Deity is just objective reality.
4. Finds Support in Reason:
Inconclusive as all such reasoning is, however, considered as rational demonstration of the reality of the Trinity, it is very far from possessing no value. It carries home to us in a very suggestive way the superiority of the Trinitarian conception of God to the conception of Him as an abstract monad, and thus brings important rational support to the doctrine of the Trinity, when once that doctrine has been given us by revelation. If it is not quite possible to say that we cannot conceive of God as eternal self-consciousness and eternal love, without conceiving Him as a Trinity, it does seem quite necessary to say that when we conceive Him as a Trinity, new fullness, richness, force are given to our conception of Him as a self-conscious, loving Being, and therefore we conceive Him more adequately than as a monad, and no one who has ever once conceived Him as a Trinity can ever again satisfy himself with a monadistic conception of God. Reason thus not only performs the important negative service to faith in the Trinity, of showing the self-consistency of the doctrine and its consistency with other known truth, but brings this positive rational support to it of discovering in it the only adequate conception of God as self-conscious spirit and living love. Difficult, therefore, as the idea of the Trinity in itself is, it does not come to us as an added burden upon our intelligence; it brings us rather the solution of the deepest and most persistent difficulties in our conception of God as infinite moral Being, and illuminates, enriches and elevates all our thought of God. It has accordingly become a commonplace to say that Christian theism is the only stable theism. That is as much as to say that theism requires the enriching conception of the Trinity to give it a permanent hold upon the human mind - the mind finds it difficult to rest in the idea of an abstract unity for its God; and that the human heart cries out for the living God in whose Being there is that fullness of life for which the conception of the Trinity alone provides.
5. Not Clearly Revealed in the Old Testament:
So strongly is it felt in wide circles that a Trinitarian conception is essential to a worthy idea of God, that there is abroad a deep-seated unwillingness to allow that God could ever have made Himself known otherwise than as a Trinity. From this point of view it is inconceivable that the Old Testament revelation should know nothing of the Trinity. Accordingly, I. A. Dorner, for example, reasons thus: "If, however - and this is the faith of universal Christendom - a living idea of God must be thought in some way after a Trinitarian fashion, it must be antecedently probable that traces of the Trinity cannot be lacking in the Old Testament, since its idea of God is a living or historical one." Whether there really exist traces of the idea of the Trinity in the Old Testament, however, is a nice question. Certainly we cannot speak broadly of the revelation of the doctrine of the Trinity in the Old Testament. It is a plain matter of fact that none who have depended on the revelation embodied in the Old Testament alone have ever attained to the doctrine of the Trinity. It is another question, however, whether there may not exist in the pages of the Old Testament turns of expression or records of occurrences in which one already acquainted with the doctrine of the Trinity may fairly see indications of an underlying implication of it. The older writers discovered intimations of the Trinity in such phenomena as the plural form of the divine name Ělōhı̄m , the occasional employment with reference to God of plural pronouns ("Let us make man in our image," Genesis 1:26; Genesis 3:22; Genesis 11:7; Isaiah 6:8 ), or of plural verbs ( Genesis 20:13; Genesis 35:7 ), certain repetitions of the name of God which seem to distinguish between God and God ( Genesis 19:27; Psalm 45:6 , Psalm 45:7; Psalm 110:1; Hosea 1:7 ), threefold liturgical formulas ( Deuteronomy 16:4; Numbers 6:24 , Numbers 6:26; Isaiah 6:3 ), a certain tendency to hypostatize the conception of Wisdom (Prov 8), and especially the remarkable phenomena connected with the appearances of the Angel of Yahweh ( Genesis 16:2-13; Genesis 22:11 , Genesis 22:16; Genesis 31:11 , Genesis 31:13; Genesis 48:15 , Genesis 48:16; Exodus 3:2 , Exodus 3:4 , Exodus 3:5; Judges 13:20-22 ). The tendency of more recent authors is to appeal, not so much to specific texts of the Old Testament, as to the very "organism of revelation" in the Old Testament, in which there is perceived an underlying suggestion "that all things owe their existence and persistence to a threefold cause," both with reference to the first creation, and, more plainly, with reference to the second creation. Passages like Psalm 33:6; Isaiah 61:1; Isaiah 63:9-12; Haggai 2:5 , Haggai 2:6 , in which God and His Word and His Spirit are brought together, co-causes of effects, are adduced. A tendency is pointed out to hypostatize the Word of God on the one hand (e.g. Genesis 1:3; Psalm 33:6; Psalm 107:20; Psalm 119:87; Psalm 147:15-18; Isaiah 55:11 ); and, especially in Ezekiel and the later Prophets, the Spirit of God, on the other (e.g. Genesis 1:2; Isaiah 48:16; Isaiah 63:10; Ezekiel 2:2; Ezekiel 8:3; Zechariah 7:12 ). Suggestions - in Isaiah for instance ( Isaiah 7:14; Isaiah 9:6 ) - of the Deity of the Messiah are appealed to. And if the occasional occurrence of plural verbs and pronouns referring to God, and the plural form of the name Ělōhı̄m , are not insisted upon as in themselves evidence of a multiplicity in the Godhead, yet a certain weight is lent them as witnesses that "the God of revelation is no abstract unity, but the living, true God, who in the fullness of His life embraces the highest variety" (Bavinck). The upshot of it all is that it is very generally felt that, somehow, in the Old Testament development of the idea of God there is a suggestion that the Deity is not a simple monad, and that thus a preparation is made for the revelation of the Trinity yet to come. It would seem clear that we must recognize in the Old Testament doctrine of the relation of God to His revelation by the creative Word and the Spirit, at least the germ of the distinctions in the Godhead afterward fully made known in the Christian revelation. And we can scarcely stop there. After all is said, in the light of the later revelation, the Trinitarian interpretation remains the most natural one of the phenomena which the older writers frankly interpreted as intimations of the Trinity; especially of those connected with the descriptions of tile Angel of Yahweh, no doubt, but also even of such a form of expression as meets us in the "Let us make man in our image" of Genesis 1:26 - for surely Genesis 1:27 : "And God created man in his own image," does not encourage us to take the preceding verse as announcing that man was to be created in the image of the angels. This is not an illegitimate reading of New Testament ideas back into the text of the Old Testament; it is only reading the text of the Old Testament under the illumination of the New Testament revelation. The Old Testament may be likened to a chamber richly furnished but dimly lighted; the introduction of light brings into it nothing which was not in it before; but it brings out into clearer view much of what is in it but was only dimly or even not at all perceived before. The mystery of the Trinity is not revealed in the Old Testament; but the mystery of the Trinity underlies the Old Testament revelation, and here and there almost comes into view. Thus, the Old Testament revelation of God is not corrected by the fuller revelation which follows it, but only perfected, extended and enlarged.
6. Prepared for in the Old Testament:
It is an old saying that what becomes patent in the New Testament was latent in the Old Testament. And it is important that the continuity of the revelation of God contained in the two Testaments should not be overlooked or obscured. If we find some difficulty in perceiving for ourselves, in the Old Testament, definite points of attachment for the revelation of the Trinity, we cannot help perceiving with great clearness in the New Testament abundant evidence that its writers felt no incongruity whatever between their doctrine of the Trinity and the Old Testament conception of God. The New Testament writers certainly were not conscious of being "setters forth of strange gods." To their own apprehension they worshipped and proclaimed just the God of Israel; and they laid no less stress than the Old Testament itself upon His unity ( John 17:3; 1 Corinthians 8:4; 1 Timothy 2:5 ). They do not, then, place two new gods by the side of Yahweh, as alike with Him to be served and worshipped; they conceive Yahweh as Himself at once Father, Son and Spirit. In presenting this one Yahweh as Father, Son and Spirit, they do not even betray any lurking feeling that they are making innovations. Without apparent misgiving they take over Old Testament passages and apply them to Father, Son and Spirit indifferently. Obviously they understand themselves, and wish to be understood, as setting forth in the Father, Son and Spirit just the one God that the God of the Old Testament revelation is; and they are as far as possible from recognizing any breach between themselves and the Fathers in presenting their enlarged conception of the Divine Being. This may not amount to saying that they saw the doctrine of the Trinity everywhere taught in the Old Testament. It certainly amounts to saying that they saw the Triune God whom they worshipped in the God of the Old Testament revelation, and felt no incongruity in speaking of their Triune God in the terms of the Old Testament revelation. The God of the Old Testament was their God, and their God was a Trinity, and their sense of the identity of the two was so complete that no question as to it was raised in their minds.
7. Presupposed Rather than Inculcated in the New Testament:
The simplicity and assurance with which the New Testament writers speak of God as a Trinity have, however, a further implication. If they betray no sense of novelty in so speaking of Him, this is undoubtedly in part because it was no longer a novelty so to speak of Him. It is clear, in other words, that, as we read the New Testament, we are not witnessing the birth of a new conception of God. What we meet with in its pages is a firmly established conception of God underlying and giving its tone to the whole fabric. It is not in a text here and there that the New Testament bears its testimony to the doctrine of the Trinity. The whole book is Trinitarian to the core; all its teaching is built on the assumption of the Trinity; and its allusions to the Trinity are frequent, cursory, easy and confident. It is with a view to the cursoriness of the allusions to it in the New Testament that it has been remarked that "the doctrine of the Trinity is not so much heard as overheard in the statements of Scripture." It would be more exact to say that it is not so much inculcated as presupposed. The doctrine of the Trinity does not appear in the New Testament in the making, but as already made. It takes its place in its pages, as Gunkel phrases it, with an air almost of complaint, already "in full completeness" (vollig fertig), leaving no trace of its growth. "There is nothing more wonderful in the history of human thought," says Sanday, with his eye on the appearance of the doctrine of the Trinity in the New Testament, "than the silent and imperceptible way in which this doctrine, to us so difficult, took its place without struggle - and without controversy - among accepted Christian truths." The explanation of this remarkable phenomenon is, however, simple. Our New Testament is not a record of the development of the doctrine or of its assimilation. It everywhere presupposes the doctrine as the fixed possession of the Christian community; and the process by which it became the possession of the Christian community lies behind the New Testament.
8. Revealed in Manifestation of Son and Spirit:
We cannot speak of the doctrine of the Trinity, therefore, if we study exactness of speech, as revealed in the New Testament, any more than we can speak of it as revealed in the Old Testament. The Old Testament was written before its revelation; the New Testament after it. The revelation itself was made not in word but in deed. It was made in the incaration of God the Son, and the outpouring of God the Holy Spirit. The relation of the two Testaments to this revelation is in the one case that of preparation for it, and in the other that of product of it. The revelation itself is embodied just in Christ and the Holy Spirit. This is as much as to say that the revelation of the Trinity was incidental to, and the inevitable effect of, the accomplishment of redemption. It was in the coming of the Son of God in the likeness of sinful flesh to offer Himself a sacrifice for sin; and in the coming of the Holy Spirit to convict the world of sin, of righteousness and of judgment, that the Trinity of Persons in the Unity of the Godhead was once for all revealed to men. Those who knew God the Father, who loved them and gave His own Son to die for them; and the Lord Jesus Christ, who loved them and delivered Himself up an offering and sacrifice for them; and the Spirit of Grace, who loved them and dwelt within them a power not themselves, making for righteousness, knew the Triune God and could not think or speak of God otherwise than as triune. The doctrine of the Trinity, in other words, is simply the modification wrought in the conception of the one only God by His complete revelation of Himself in the redemptive process. It necessarily waited, therefore, upon the completion of the redemptive process for its revelation, and its revelation, as necessarily, lay complete in the redemptive process.
From this central fact we may understand more fully several circumstances connected with the revelation of the Trinity to which allusion has been made. We may from it understand, for example, why the Trinity was not revealed in the Old Testament. It may carry us a little way to remark, as it has been customary to remark since the time of Gregory of Nazianzus, that it was the task of the Old Testament revelation to fix firmly in the minds and hearts of the people of God the great fundamental truth of the unity of the Godhead; and it would have been dangerous to speak to them of the plurality within this unity until this task had been fully accomplished. The real reason for the delay in the revelation of the Trinity, however, is grounded in the secular development of the redemptive purpose of God: the times were ripe for the revelation of the Trinity in the unity of the Godhead until the fullness of the time had come for God to send forth His Son unto redemption, and His Spirit unto sanctification. The revelation in word must needs wait upon the revelation in fact, to which it brings its necessary explanation, no doubt, but from which also it derives its own entire significance and value. The revelation of a Trinity in the divine unity as a mere abstract truth without relation to manifested fact, and without significance to the development of the kingdom of God, would have been foreign to the whole method of the divine procedure as it lies exposed to us in the pages of Scripture. Here the working-out of the divine purpose supplies the fundamental principle to which all else, even the progressive stages of revelation itself, is subsidiary; and advances in revelation are ever closely connected with the advancing accomplishment of the redemptive purpose. We may understand also, however, from the same central fact, why it is that the doctrine of the Trinity lies in the New Testament rather in the form of allusions than in express teaching, why it is rather everywhere presupposed, coming only here and there into incidental expression, than formally inculcated. It is because the revelation, having been made in the actual occurrences of redemption, was already the common property of all Christian hearts. In speaking and writing to one another, Christians, therefore, rather spoke out of their common Trinitarian consciousness, and reminded one another of their common fund of belief, than instructed one another in what was already the common property of all. We are to look for, and we shall find, in the New Testament allusions to the Trinity, rather evidence of how the Trinity, believed in by all, was conceived by the authoritative teachers of the church, than formal attempts, on their part, by authoritative declarations, to bring the church into the understanding that God is a Trinity.
9. Implied in the Whole New Testament:
The fundamental proof that God is a Trinity is supplied thus by the fundamental revelation of the Trinity in fact: that is to say, in the incarnation of God the Son and the outpouring of God the Holy Spirit. In a word, Jesus Christ and the Holy Spirit are the fundamental proof of the doctrine of the Trinity. This is as much as to say that all the evidence of whatever kind, and from whatever source derived, that Jesus Christ is God manifested in the flesh, and that the Holy Spirit is a Divine Person, is just so much evidence for the doctrine of the Trinity; and that when we go to the New Testament for evidence of the Trinity we are to seek it, not merely in the scattered allusions to the Trinity as such, numerous and instructive as they are, but primarily in the whole mass of evidence which the New Testament provides of the Deity of Christ and the divine personality of the Holy Spirit. When we have said this, we have said in effect that the whole mass of the New Testament is evidence for the Trinity. For the New Testament is saturated with evidence of the Deity of Christ and the divine personality of the Holy Spirit, Precisely what the New Testament is, is the documentation of the religion of the incarnate Son and of the outpoured Spirit, that is to say, of the religion of the Trinity, and what we mean by the doctrine of the Trinity is nothing but the formulation in exact language of the conception of God presupposed in the religion of the incarnate Son and outpoured Spirit. We may analyze this conception and adduce proof for every constituent element of it from the New Testament declarations. We may show that the New Testament everywhere insists on the unity of the Godhead; that it constantly recognizes the Father as God, the Son as God and the Spirit as God; and that it cursorily presents these three to us as distinct Persons. It is not necessary, however, to enlarge here on facts so obvious. We may content ourselves with simply observing that to the New Testament there is but one only living and true God; but that to it Jesus Christ and the Holy Spirit are each God in the fullest sense of the term; and yet Father, Son and Spirit stand over against each other as I, and Thou, and He. In this composite fact the New Testament gives us the doctrine of the Trinity. For the doctrine of the Trinity is but the statement in wellguarded language of this composite fact. Through out the whole course of the many efforts to formulate the doctrine exactly, which have followed one another during the entire history of the church, indeed, the principle which has ever determined the result has always been determination to do justice in conceiving the relations of God the Father, God the Son and God the Spirit, on the one hand to the unity of God, and, on the other, to the true Deity of the Son and Spirit and their distinct personalities. When we have said these three things, then - that there is but one God, that the Father and the Son and the Spirit is each God, that the Father and the Son and the Spirit is each a distinct person - we have enunciated the doctrine of the Trinity in its completeness.
That this doctrine underlies the whole New Testament as its constant presupposition and determines everywhere its forms of expression is the primary fact to be noted. We must not omit explicitly to note, however, that it now and again also, as occasion arises for its incidental enunciation, comes itself to expression in more or less completeness of statement. The passages in which the three Persons of the Trinity are brought together are much more numerous than, perhaps, is generally supposed; but it should be recognized that the formal collocation of the elements of the doctrine naturally is relatively rare in writings which are occasional in their origin and practical rather than doctrinal in their immediate purpose. The three Persons already come into view as Divine Persons in the annunciation of the birth of our Lord: 'The Holy Ghost shall come upon thee,' said the angel to Mary, 'and the power of the Most High shall overshadow thee: wherefore also the holy thing which is to be born shall be called the Son of God' ( Luke 1:35 margin; compare Matthew 1:18 ff). Here the Holy Ghost is the active agent in the production of an effect which is also ascribed to the power of the Most High, and the child thus brought into the world is given the great designation of "Son of God." The three Persons are just as clearly brought before us in the account of Matthew ( Matthew 1:18 ff), though the allusions to them are dispersed through a longer stretch of narrative, in the course of which the Deity of the child is twice intimated ( Matthew 1:21 : 'It is He that shall save His people from their sins'; Matthew 1:23 : 'They shall call His name Immanuel; which is, being interpreted, God-with-us ') In the baptismal scene which finds record by all the evangelists at the opening of Jesus' ministry ( Matthew 3:16 , Matthew 3:17; Mark 1:10 , Mark 1:11; Luke 3:21 , Luke 3:22; John 1:32-34 ), the three Persons are thrown up to sight in a dramatic picture in which the Deity of each is strongly emphasized. From the open heavens the Spirit descends in visible form, and 'a voice came out of the heavens, Thou art my Son, the Beloved, in whom I am well pleased.' Thus care seems to have been taken to make the advent of the Son of God into the world the revelation also of the Triune God, that the minds of men might as smoothly as possible adjust themselves to the preconditions of the divine redemption which was in process of being wrought out.
10. Conditions the Whole Teaching of Jesus:
With this as a starting-point, the teaching of Jesus is conditioned throughout in a Trinitarian way. He has much to say of God His Father, from whom as His Son He is in some true sense distinct, and with whom He is in some equally true sense one. And He has much to say of the Spirit, who represents Him as He represents the Father, and by whom He works as the Father works by Him. It is not merely in the Gospel of John that such representations occur in the teaching of Jesus. In the Synoptics, too, Jesus claims a Sonship to God which is unique ( Matthew 11:27; Matthew 24:36; Mark 13:32; Luke 10:22; in the following passages the title of "Son of God" is attributed to Him and accepted by Him: Matthew 4:6; Matthew 8:29; Matthew 14:33; Matthew 27:40 , Matthew 27:43 , Matthew 27:44; Mark 3:11; Mark 12:6-8; Mark 15:39; Luke 4:41; Luke 22:70; compare John 1:34 , John 1:49; John 9:35; John 11:27 ), and which involves an absolute community between the two in knowledge, say, and power: both Matthew ( Matthew 11:27 ) and Luke ( Luke 10:22 ) record His great declaration that He knows the Father and the Father knows Him with perfect mutual knowledge: "No one knoweth the Son, save the Father; neither doth any know the Father, save the Son." In the Synoptics, too, Jesus speaks of employing the Spirit of God Himself for the performance of His works, as if the activities of God were at His disposal: "I by the Spirit of God" - or as Luke has it, "by the finger of God - cast out demons" ( Matthew 12:28; Luke 11:20; compare the promise of the Spirit in Mark 13:11; Luke 12:12 ).
11. Father and Son in Johannine Discourses:
It is in the discourses recorded in John, however, that Jesus most copiously refers to the unity of Himself, as the Son, with the Father, and to the mission of the Spirit from Himself as the dispenser of the divine activities. Here He not only with great directness declares that He and the Father are one ( John 10:30; compare John 17:11 , John 17:21 , John 17:22 , John 17:25 ) with a unity of interpenetration ("The Father is in me, and I in the Father," John 10:38; compare John 16:10 , John 16:11 ), so that to have seen Him was to have seen the Father ( John 14:9; compare John 15:21 ); but He removes all doubt as to the essential nature of His oneness with the Father by explicitly asserting His eternity ("Before Abraham was born, I am," John 8:58 ), His co-eternity with God ("had with thee before the world was," John 17:5; compare John 17:18; John 6:62 ), His eternal participation in the divine glory itself ("the glory which I had with thee," in fellowship, community with Thee "before the world was," John 17:5 ). So clear is it that in speaking currently of Himself as God's Son ( John 5:25; John 9:35; John 11:4; compare John 10:36 ), He meant, in accordance with the underlying significance of the idea of sonship in Semitic speech (founded on the natural implication that whatever the father is that the son is also; compare John 16:15; John 17:10 ), to make Himself, as the Jews with exact appreciation of His meaning perceived, "equal with God" ( John 5:18 ), or, to put it brusquely, just "God" ( John 10:33 ). How He, being thus equal or rather identical with God, was in the world, He explains as involving a coming forth (ἐξῆλθον , exḗlthon ) on His part, not merely from the presence of God (ἀπό , apó , John 16:30; compare John 13:3 ) or from fellowship with God (παρά , pará , John 16:27; John 17:8 ), but from out of God Himself (ἐκ , ek , John 8:42; John 16:28 ). And in the very act of thus asserting that His eternal home is in the depths of the Divine Being, He throws up, into as strong an emphasis as stressed pronouns can, convey, His personal distinctness from the Father. 'If God were your Father,' says Hebrews (8:42), 'ye would love me: for I came forth and am come out of God; for neither have I come of myself , but it was He that sent me.' Again, He says ( John 16:26 , John 16:27 ): 'In that day ye shall ask in my name: and I say not unto you that I will make request of the Father for you; for the Father Himself loveth you, because ye have loved me, and have believed that it was from fellowship with the Father that I came forth; I came from out of the Father, and have come into the world.' Less pointedly, but still distinctly, He says again ( John 17:8 ): They know of a truth that it was from fellowship with Thee that I came forth, and they believed that it was Thou that didst send me.' It is not necessary to illustrate more at large a form of expression so characteristic of the discourses of our Lord recorded by Jn that it meets us on every page: a form of expression which combines a clear implication of a unity of Father and Son which is identity of Being, and an equally clear implication of a distinction of Person between them such as allows not merely for the play of emotions between them, as, for instance, of love ( John 17:24; compare John 15:9 ( John 3:35 ); John 14:31 ), but also of an action and reaction upon one another which argues a high measure, if not of exteriority, yet certainly of exteriorization. Thus, to instance only one of the most outstanding facts of our Lord's discourses (not indeed confined to those in John's Gospel, but found also in His sayings recorded in the Synoptists, as e.g. Luke 4:43 (compare parallel Mark 1:38 ); Luke 9:48; Luke 10:16; Luke 4:34; Luke 5:32; Luke 7:19; Luke 19:10 ), He continually represents Himself as on the one hand sent by God, and as, on the other, having come forth from the Father (e.g. John 8:42; John 10:36; John 17:3; John 5:23 , et saepe ).
12. Spirit in Johannine Discourses:
It is more important to point out that these phenomena of interrelationship are not confined to the Father and Son, but are extended also to the Spirit. Thus, for example, in a context in which our Lord had emphasized in the strongest manner His own essential unity and continued interpenetration with the Father (" If ye had known me, ye would have known my Father also"; "He that hath seen me hath seen the Father"; "I am in the Father, and the Father in me"; "The Father abiding in me doeth his works," John 14:7 , John 14:9 , John 14:10 ), we read as follows ( John 14:16-26 ): 'And I will make request of the Father , and He shall ive you another (thus sharply distinguished from Our Lord as a distinct Person) Advocate, that He may be with you forever, the Spirit of Truth ... He abideth with you and shall be in you. I will not leave you orphans; I come unto you.... In that day ye shall know that I am in the Father.... If a man love me, he will keep my word; and my Father will love him and we (that is, both Father and Son) will come unto him and make our abode with him.... These things have I spoken unto you while abiding with you. But the Advocate, the Holy Spirit, whom the Father will send in my name, He shall teach you all things, and bring to your remembrance all that I said unto you.' It would be impossible to speak more distinctly of three who were yet one. The Father, Son and Spirit are constantly distinguished from one another - the Son makes request of the Father, and the Father in response to this request gives an Advocate, "another" than the Son, who is sent in the Son's name. And yet the oneness of these three is so kept in sight that the coming of this "another Advocate" is spoken of without embarrassment as the coming of the Son Himself ( John 14:18 , John 14:19 , John 14:20 , John 14:21 ), and indeed as the coming of the Father and the Son ( John 14:23 ). There is a sense, then, in which, when Christ goes away, the Spirit comes in His stead; there is also a sense in which, when the Spirit comes, Christ comes in Him; and with Christ's coming the Father comes too. There is a distinction between the Persons brought into view; and with it an identity among them; for both of which allowance must be made. The same phenomena meet us in other passages. Thus, we read again ( John 15:26 ): But when there is come the Advocate whom I will send unto you from (fellowship with) the Father, the Spirit of Truth, which goeth forth from (fellowship with) the Father, He shall bear witness of me.' In the compass of this single verse, it is intimated that the Spirit is personally distinct from the Son, and yet, like Him, has His eternal home (in fellowship) with the Father, from whom He, like the Son, comes forth for His saving work, being sent thereunto, however, not in this instance by the Father, but by the Son.
This last feature is even more strongly emphasized in yet another passage in which the work of the Spirit in relation to the Son is presented as closely parallel with the work of the Son in relation to the Father ( John 16:5 ff). 'But now I go unto Him that sent me ... Nevertheless I tell you the truth; it is expedient for you that I go away; for, if I go not away the Advocate will not come unto you; but if I go I will send Him unto you. And He , after He is come, will convict the world ... of righteousness because I go to the Father and ye behold me no more.... I have yet many things to say unto you, but ye cannot bear them now. Howbeit when He , the Spirit of truth is come, He shall guide you into all the truth; for He shall not speak from Himself; but what things soever He shall hear, He shall speak, and He shall declare unto you the things that are to come. He shall glorify me : for He shall take of mine and shall show it unto you. All things whatsoever the Father hath are mine : therefore said I that He taketh of mine, and shall declare it unto you.' Here the Spirit is sent by the Son, and comes in order to complete and apply the Son's work, receiving His whole commission from the Son - not, however, in derogation of the Father, because when we speak of the things of the Son, that is to speak of the things of the Father.
It is not to be said, of course, that the doctrine of the Trinity is formulated in passages like these, with which the whole mass of our Lord's discourses in John are strewn; but it certainly is presupposed in them, and that is, considered from the point of view of their probative force, even better. As we read we are kept in continual contact with three Persons who act, each as a distinct person, and yet who are in a deep, underlying sense, one. There is but one God - there is never any question of that - and yet this Son who has been sent into the world by God not only represents God but is God, and this Spirit whom the Son has in turn sent unto the world is also Himself God. Nothing could be clearer than that the Son and Spirit are distinct Persons, unless indeed it be that the Son of God is just God the Son and the Spirit of God just God the Spirit.
13. The Baptismal Formula:
Meanwhile, the nearest approach to a formal announcement of the doctrine of the Trinity which is recorded from our Lord's lips, or, perhaps we may say, which is to be found in the whole compass of the New Testament, has been preserved for us, not by John, but by one of the synoptists. It too, however, is only incidentally introduced, and has for its main object something very different from formulating the doctrine of the Trinity. It is embodied in the great commission which the resurrected Lord gave His disciples to be their "marching orders" "even unto the end of the world": "Go ye therefore, and make disciples of all the nations, baptizing them into the name of the Father and of the Son and of the Holy Spirit" ( Matthew 28:19 ). In seeking to estimate the significance of this great declaration, we must bear in mind the high solemnity of the utterance, by which we are required to give its full value to every word of it. Its phrasing is in any event, however, remarkable. It does not say, "In the names (plural) of the Father and of the Son and of the Holy Ghost"; nor yet (what might be taken to be equivalent to that), "In the name of the Father, and in the name of the Son, and in the name of the Holy Ghost," as if we had to deal with three separate Beings. Nor, on the other hand does it say, "In the name of the Father, Son and Holy Ghost," as if "the Father, Son and Holy Ghost" might be taken as merely three designations of a single person. With stately impressiveness it asserts the unity of the three by combining them all within the bounds of the single Name; and then throws up into emphasis the distinctness of each by introducing them in turn with the repeated article: "In the name of the Father, and of the Son, and of the Holy Ghost (the King James Version). These three, the Father, and the Son, and the Holy Ghost, each stand in some clear sense over against the others in distinct personality: these three, the Father, and the Son, and the Holy Ghost, all unite in some profound sense in the common participation of the one Name. Fully to comprehend the implication of this mode of statement, we must bear in mind, further, the significance of the term, "the name," and the associations laden with which it came to the recipients of this commission. For the Hebrew did not think of the name, as we are accustomed to do, as a mere external symbol; but rather as the adequate expression of the innermost being of its bearer. In His Name the Being of God finds expression; and the Name of God - "this glorious and fearful name, Yahweh thy God" ( Deuteronomy 28:58 ) - was accordingly a most sacred thing, being indeed virtually equivalent to God Himself. It is no solecism, therefore, when we read ( Isaiah 30:27 ), "Behold, the name of Yahweh cometh"; and the parallelisms are most instructive when we read ( Isaiah 59:19 ): 'So shall they fear the Name of Yahweh from the west, and His glory from the rising of the sun; for He shall come as a stream pent in which the Spirit of Yahweh driveth.' So pregnant was the implication of the Name, that it was possible for the term to stand absolutely, without adjunction of the name itself, as the sufficient representative of the majesty of Yahweh: it was a terrible thing to 'blaspheme the Name' ( Leviticus 24:11 ). All those over whom Yahweh's Name was called were His, His possession to whom He owed protection. It is for His Name's sake, therefore, that afflicted Judah cries to the Hope of Israel, the Saviour thereof in time of trouble: 'O Yahweh, Thou art in the midst of us, and Thy Name is called upon us; leave us not' ( Jeremiah 14:9 ); and His people find the appropriate expression of their deepest shame in the lament, 'We have become as they over whom Thou never barest rule; as they upon whom Thy Name was not called' ( Isaiah 63:19 ); while the height of joy is attained in the cry, 'Thy Name, Yahweh, God of Hosts, is called upon me' ( Jeremiah 15:16; compare 2 Chronicles 7:14; Daniel 9:18 , Daniel 9:19 ). When, therefore, our Lord commanded His disciples to baptize those whom they brought to His obedience "into the name of ...," He was using language charged to them with high meaning. He could not have been understood otherwise than as substituting for the Name of Yahweh this other Name "of the Father, and of the Son, and of the Holy Ghost"; and this could not 'possibly have meant to His disciples anything else than that Yahweh was now to be known to them by the new Name, of the Father, and the Son, and the Holy Ghost. The only alternative would have been that, for the community which He was rounding, Jesus was supplanting Yahweh by a new God; and this alternative is no less than monstrous. There is no alternative, therefore, to understanding Jesus here to be giving for His community a new Name to Yahweh, and that new Name to be the threefold Name of "th
Cyclopedia of Biblical, Theological and Ecclesiastical Literature 
The doctrine of the Trinity in the godhead includes the three following particulars, viz. (a) There is only one God, one divine nature; (b) but in this divine nature there is the distinction of Father, Son, and Holy Ghost, as three (subjects or persons); and (c) these three-have equally, and in common with one another, the nature and perfection of supreme divinity. It was the custom in former times for theologians to blend their own speculations and those of others with the statement of the Bible doctrine. It is customary now to exhibit first the simple doctrine of the Bible, and afterwards, in a separate part, the speculations of the learned respecting it.
I. The Biblical Doctrine. — It has always been allowed that the doctrine of the Trinity was not fully revealed before the time of Christ, and is clearly taught only in the New Test. Yet, while it is true (1) that if the New Test. did not exist we could not derive the doctrine of the Trinity from the Old- Test. alone, it is equally true (2) that by the manner of God's revelation of himself in the Old Test. the way was prepared for the more full disclosure of his nature that was afterwards made. But (3) respecting the intimate connection of these persons, or respecting other distinctions which belong to the doctrine of the Trinity, there is nothing said in the Old Test. While in each particular text allusion is made to a trinity or plurality in God, yet these texts are so many in number and so various in kind that they impress one with the opinion that such a plurality in God is indicated in the Old Test., though it is not fully developed or clearly defined.
(I.) The texts of the Old Test. may be arranged in the following classes:
1. Those giving the names of God in the plural form, and thus seeming to indicates a plurality of his nature, of which קְדוֹשַׁים אֲדֹנָי אֵֹלהַים are cited as examples; but as these may be only the pluralis majestaticus of the Oriental languages, they afford no certain proof.
2. Texts in which God speaks of himself in the plural. The plural in many of these cases can be accounted for from the use of the plural nouns אֲדֹנָי אֵֹלהַים , etc. Philo thinks ( De Opif. Mundi, p. 17) that in the expression "Let us make man" ( Genesis 1:26), God addresses the angels. It is not uncommon in Hebrew for kings to speak of themselves in the plural ( 1 Kings 12:9; 2 Chronicles 10:9; Ezra 4:18). In Isaiah 6:8 God asks, who will go for us ( לָנוּ ), where the plural form may be explained either as the Pluralis Majestaticus, or as denoting an assembly for consultation.
3. Texts in which יְהוָֹה (Jehovah) is distinguished from אֲלֹהַים (Elohim).These texts do not, however, furnish any decisive proof; for in the simplicity of ancient style the noun is often repeated instead of using the pronoun; and so, From Jehovah may mean From Himself, etc. Further, the name אֵֹלהַים (Elohim) is sometimes given to earthly kings, and does not, therefore, necessarily prove that the person to whom it is given must be of the divine nature.
4. Texts in which express mention is made of the Son Of God and of the Holy Spirit.
(a.) Of The Son Of God. — The principal text of this class is Psalms 2:7, "Thou art my son; this day have I begotten thee;" comp. Psalms 72:1; Psalms 89:27. This Psalm was understood by the Jews and by the writers of the New Test. to relate to the Messiah. But the name Son of God was not infrequently given to kings; it is not, therefore, nomen essentice, but dignitatis Messiance. The passage would then mean, "Thou art the king (Messiah) of my appointment; this day have I declared thee such." In this psalm, therefore, the Messiah is rather exhibited as king, divinely appointed ruler and head of the Church, than as belonging to the divine nature.
(b.) Of The Holy Spirit. — There are many texts of this class, but none from which, taken by themselves, the personality of the Holy Spirit can be proved. In these texts the Term Holy Spirit may mean (1) the divine nature in general; (2) particular divine attributes, as omnipotence, knowledge, or omniscience; (3) the divine agency, which is its more common meaning. Isaiah 48:16, "And now Jehovah (the Father) and his Spirit (Holy Ghost) hath sent me" (the Messiah), is supposed to teach the whole doctrine of the Trinity. But the expression "and his Spirit" is used by the prophets to mean the Direct, Immediate Command of God. . To say, then, the Lord and his Spirit hath sent me is the same as to say, the Lord hath sent me by a direct, immediate command.
5. Texts in which Three persons are expressly mentioned, or in which there is a clear reference to the number Three ( Numbers 6:24; Psalms 33:6; Isaiah 6:3). But the repetition of the Word Jehovah in the one text is not an undeniable proof of the Trinity; and in the other, the Word Of His Mouth means nothing more than his Command ; And in the last text the threefold repetition of the word Holy may have been by three choirs, all uniting in the last words, "The whole earth is full of thy glory."
Thus it appears that none of the passages cited from the Old Test. in proof of the Trinity are conclusive when taken by themselves; but, as was before stated, when they are all taken together, they convey the impression that at least a plurality in the godhead was obscurely indicated in the Jewish Scriptures.
(II.) Since we do not find in the Old Test. clear or decided proof upon this subject, we must now turn to the New Test. The texts relating to the doctrine of the Trinity may be divided into two classes — those in which the Father, Son, and Holy Spirit are mentioned in connection, and those in which these three subjects are mentioned separately, and in which their nature and mutual relation are more particularly described.
1. The first class of texts, taken by itself, proves only that there are the three subjects named, and that there is a difference between them; that the Father in certain respects differs from the Son, etc.; but it does not prove, by itself, that all the three belong necessarily to the divine nature, and possess equal divine honor. In proof of this, the second class of texts must be adduced. The following texts are placed in this class:
Matthew 18:18-20. This text, however, taken by itself, would not prove decisively either the Personality of the three subjects mentioned, or their Equality or Divinity. For ( A ) the subject into which one is baptized is not necessarily a Person, but may be a Doctrine or Religion. ( B ) The person in whom one is baptized is not necessarily God, as 1 Corinthians 1:13, "Were ye baptized in the name of Paul?" ( C ) The connection of these three subjects does not prove their Personality or Equality. We gather one thing from the text, viz. that Christ considered the doctrine respecting Father, Son, and Holy Ghost as a fundamental doctrine of his religion, because he requires all his followers to be bound to a profession of it when admitted by baptism into the Church.
1 Peter 1:2 : "Elect according to the foreknowledge of God the Father, through sanctification of the Spirit, unto obedience and sprinkling of the blood of Jesus Christ." From what is here said of the Holy Spirit, it does not necessarily follow that he is a personal subject; nor, from the predicates here ascribed to Christ, that he is necessarily divine. This passage, therefore, taken by itself, is insufficient.
2 Corinthians 13:14, "The grace of the Lord Jesus Christ, and the love of God, and the communion of the Holy Ghost, be with you all." Here we might infer, from the parallelism of the third member of the passage with the two former, the Personality of the Holy Spirit; but we could not justly infer that they possessed Equal Authority, or the same nature.
John 14:26 offers three different personal subjects, viz. the Comforter, the Father, and Christ; but it is not sufficiently proven from this passage that these three subjects have equal divine honor, and belong to one divine nature.
Matthew 3:16-17 has been considered a very strong proof-text for the whole doctrine of the Trinity. But though three personal subjects are mentioned, viz. the voice of the Father, the symbol of the Holy Spirit, and Christ, yet nothing is here said respecting their nature.
1 John 5:7-8 are generally admitted to be spurious; and, even if allowed to be genuine, they do not determine the nature and essential connection of the three subjects mentioned.
2. We now turn to the second class of texts; viz. those in which the Father. Son, and Holy Ghost are separately mentioned, and in which their nature and mutual relation are taught. These texts prove ( A ) that the Son and Holy Spirit, according to the doctrine of the New Test., are divine, or belong to the one divine nature; and ( B ) that the three subjects are personal and equal.
(1.) The Deity Of The Father. — When the term Father is applied to God, it often designates the whole godhead, or the whole divine nature; as Θεὸς Ὁ Πᾷτήρ , , 1 Corinthians 8:4-6; John 17:1-3. He is often called Θεὸς Καὶ Πατήρ , i.e. Θεὸς Ὁ Πατήρ , or Θεὸς Θεὸς Ὅς Ἐστι Πατήρ , as Galatians 1:4, All the arguments, therefore, which prove the existence of God prove also the deity of the Father.
(2.) The Deity Of Christ. — To prove the deity of Christ we present three classes of texts.
(a.) The following are the principal texts in which divine names are given to Christ:
John 1:1-2. Christ is here called Ὁ Λόγος (the Word), which signified among the Jews and other ancient people, when applied to God, Everything By Which God Reveals Himself To Men, and makes known to them his will. Hence those who made known the divine will to men were called by the Hellenists Λόγοι . It was probably on this account that John declared Jesus to be the Logos which existed Ἐν Ἀρχῇ ; that The Logos Was With God, and The Logos Was God. In this passage the principal proof does not lie in the word Λόγος , nor even in the word Θεός , which in a larger sense is often applied to kings and earthly rulers; but to what is predicated of the Λόγος , viz. that he existed from eternity with God, that the world was made by him, etc.
John 20:28. Here Thomas, convinced at last that Christ was actually risen from the dead, thus addresses him, "My Lord and my God." This must not be considered an exclamation of surprise or wonder, as some have understood it; for it is preceded by the phrase Ειπεν Αὐτῷ , he said this to him." Thomas probably remembered what Jesus had often said respecting his superhuman origin ( John 5:8; John 5:10; John 5:17), and he now saw it all confirmed by his resurrection from the dead.
Philippians 2:6, "Who, being in the form of God, thought it not robbery to be equal with God." There it is said of Christ that he is Ἴσα Θεῷ , Deo Cequalis ; not Ὅμοιος Θεῷ , Ἀντίθεος , Θεοείκελος , similis Deo-terms applied by Homer to kings and heroes. The term Ἴσος Θεῷ , on the contrary, is never applied to a finite or created being. Hence the Jews (John 18) considered it as blasphemy in Christ to make himself Ἴσον Θεῷ .
John 10:28-30, "I and my Father are one." These words are not to be understood to denote so much an equality of nature as unanimity of feeling and purpose. Still the passage is quite remarkable; because Christ professes to do his work In Common With his Father; and that is more than any man, prophet, or even angel is ever said in the Bible to do. That being one with God, therefore, which Jesus here asserts for himself is something peculiar, which belongs to him only as he is a being of a higher nature.
Titus 2:13, "We expect the glorious appearance," etc. In this passage, since Τοῦ is omitted before Σωτῆρος , both Μεγάλου Θεοῦ and Σωτῆρος must be construed in apposition with Ι᾿Ησοῦ Χριστοῦ . Moreover, Ἐπιφάνεια is the word by which the solemn coming of Christ is appropriately designated.
In some of the texts in which Christ is called the Son of God, the name is used in three different senses  Messiah or king, a title very commonly given to the Messiah by the Jews (see Matthew 16:16; Luke 9:20; Matthew 27:40; Luke 23:35; see also Mark 13:32; 1 Corinthians 15:28);  the higher nature of Christ ( John 5:17 sq.; John 10:30; John 10:33; John 20:31; Romans 1:3-4);  he is also called the Son of God ( Luke 1:35), to designate the immediate power of God in the miraculous production of his, human nature.
(b.) Texts in which divine attributes and works are ascribed to Christ. It is not necessary to find texts to prove that all the divine attributes are ascribed to Christ. These attributes cannot be separated; and if one of them is ascribed to Christ in the Bible, the conclusion is inevitable that he must possess all the rest. The following attributes and works are distinctly ascribed to Christ in the Scriptures:
Eternity ( John 1:1; John 8:58; John 17:5; Colossians 1:17).
Creation And Preservation Of The World ( John 1:1-3; John 1:10; Colossians 1:16; Hebrews 1:10 [where Psalms 102:26 is quoted and applied to Christ]; Hebrews 2:10).
(c.) Texts in which divine honor is required for Christ. The following are the principal texts of this class; John 5:23, All men should honor the Son, even as they honor the Father;" Acts 1:24; Acts 7:59; 2 Corinthians 12:8, where Christ is approached in prayer; and those in which the apostles refer to Christ the texts of the Old Test. that speak of the honor and worship of God, e.g. Hebrews 1:6 from Psalms 97:7; also Romans 14:11 from Isaiah 45:3; Philippians 2:10; 2 Corinthians 5:8-11; 2 Timothy 4:17-18.
(3.) The third point in the discussion of this doctrine is the personality and divinity of the Holy Spirit; for a full discussion of which (See Holy Ghost).
II. History Of The Doctrine. — Respecting the Manner in which the Father, the Son, and the Holy Ghost make one God, the Scripture teaches nothing, since the subject is of such a nature as not to admit of its being explained to us. It is therefore to be expected that theologians should differ widely in their opinions respecting it, and that in their attempts to illustrate it they should have pursued various methods.
1 . As Held By The Primitive Christians. — For the first age the Scripture is sufficient evidence of the Christians' practice. For, not to insist upon the precept of honoring the Son as they honored the Father; or the form of baptism, in which they were commanded to join the Father, Son, and Holy Ghost in one act of worship; or the injunction to believe in the Son as they believed in the Father, let reference be made only to their example and practice. Stephen, the protomartyr, when he was sealing his confession with his blood, prayed to Christ, "Lord Jesus, receive my spirit," and "Lord, lay not this sin to their charge" ( Acts 7:59-60). Paul asserts that he baptized only in the name of Christ ( 1 Corinthians 1:13). Notice also his constant use of the name of Christ in invocation. There is the well known fact that the early believers were known as those who called on the name of Christ ( Acts 9:14; Acts 9:21; 1 Corinthians 1:2; 2 Timothy 2:22).
2. As Held In The 2Nd And 3Rd Centuries. — Towards the end of the 1st century, and during the 2d, many learned men came over both from Judaism and paganism to Christianity. These brought with them into the Christian schools of theology their Platonic ideas and phraseology, and they especially borrowed from the philosophical writings of Philo. As was very natural, they confined themselves, in their philosophizing respecting the Trinity, principally to the Logos; connecting the same ideas with the name Λόγος as had been done before by Philo and other Platonists. Differing on several smaller points, they agreed perfectly in the following general views, viz.: the Logos existed before the creation of the world; he was begotten, however, by God, and sent forth from him. By this Logos the Neo-Platonists understood the infinite Understanding of God, belonging from eternity to his nature as a Power, but that, agreeably to the divine will, it began to exist out of the divine nature. It is therefore different from God, and yet, as begotten of him, is entirely divine. By means of this Logos they supposed that God at first created, and now preserves and governs, the universe. Their views respecting the Holy Spirit are far less clearly expressed, though most of them considered him a substance emanating from the Father and the Son, to whom, on this account, divinity must be ascribed. These philosophical Christians asserted rather the divineness of the Son and Spirit, and their divine origin, than their equal deity with the Father. Justin Martyr expressly declares that the Son is in God what the understanding ( Νοῦς ) is in man, and that the Holy Spirit is that divine power to act and execute which Plato calls Ἀρετή . With this representation Theophilus of Antioch, Clemens of Alexandria, and Origen substantially agree. According to Tertullian, the persons of the Trinity are gradus, formae species unius Dei. Thus we find that the belief in the subordination of the-Son to the Father, for which Arianism is the later name, was commonly received by most of those fathers of the 2d and 3d centuries who assented, in general, to the philosophy of Plato. Another class of learned, philosophizing Christians substituted another theory on the subject of the Trinity, which, however, was nonetheless formed rather from their philosophical ideas than from, the instructions of the Bible. Among the writers of this class was Praxeas, of the 2rd century, who contended that the Father, Son, and Spirit' were not distinguished from each other as individual subjects; but that God was called Father, so far as he was creator and governor of the world; Son ( Λόγος ), so far as he had endowed the man Jesus with extraordinary powers, etc. He, in accordance with this view, denied any Higher, Preexisting nature in Christ; and with him agreed Artemon, Noetus, and Beryllus of Bostra. Sabellius regarded the terms Father, Son, and Holy Spirit as merely describing different divine works, and various modes of divine revelation.
In the following table the writers of the first three centuries on the subject of the Trinity are ranged according to their opinions:
Theophilus of Antioch
Paul of Samosata
Beryillus of Bostra
Among the terms introduced in the discussion of the doctrine of the Trinity during this period the following are the most common, viz.
(1.) Τρίας , introduced by Theophilus of Antioch in the 2d century, and often used by Origen in the 3d century. Tertullian translated it into Latin by the word Trinitas, of which the English word is an exact rendering.
(2.) Οὐσία , Ὑπόστασις . These terms were not sufficiently distinguished from each other by the Greek fathers of the 2nd and 3rd centuries, and were often used by them as entirely synonymous. By the word Ὑπόστασις , the older Greek fathers understood only a really existing subject, in opposition to a nonentity, or to a merely ideal existence; in which sense they also not infrequently used the word Οὐσία .
(3.) Persona. This word was first employed by Tertullian, and by it he means An Individual, a single being; distinguished from others by certain peculiar qualities, attributes, and relations; and so he calls Pater, Filius, Spiritus Sanctus, Tres Personae (three persons), at the same time that he ascribes to them Unitas Substantiac (unity of substance), because they belong to the divine nature ( Οὐσία ) existing from eternity.
We call attention to the following as shedding light upon the practice of the Church during this period. Pliny, a judge under Trajan, in the beginning of the 2d century took the confessions of some accused Christians, and says, "They declared that they were used to meet on a certain day before it was light, and, among other parts of their worship, sing a hymn to Christ as their God." Polycarp (Ep. ad Philip. n. 12) joins God the Father and the Son together in his prayers for grace and benediction upon men. Justin Martyr answering, in his Second Apology, the charge of atheism brought against them by the heathen answers. "That they worshipped and adored still the God of righteousness and his Son, as also the Holy Spirit of prophecy." Athenagoras answers the charge of atheism after the same manner. Similar testimony is afforded by the writings of Lucian the heathen, Theophilus of Antioch. Clemens Alexandrinus, Origen, Novatian, and others, illustrating the practice of the Church in paying divine honors to the Son and Holy Spirit.
3. The Trinity As Held In The 4Th Century. — It had already been settled, by many councils held during the 3d century, and in the symbols which they had adopted in opposition to Sabellius and Paul of Samosata, that the Father must be regarded as Really distinguished from the Son, and the Holy Spirit as distinguished from both; The relation, however, of the three persons of the Trinity, and the question in what the distinction between them properly consists, not having been discussed, these subjects were left undetermined by the decisions of councils and symbols. Different opinions prevailed, and learned men were left to express themselves according to their convictions.
Origen and his followers maintained, against the Sabellians, that there were in God Τρεῖς Ὑποστάσείς ' (three persons), but , Μία Οὐσία (one substance) common to the three. Few had as yet taught the entire Equality of these three persons, but had allowed, in accordance with their Platonic principles, that the Son, though belonging to the divine nature, was yet subordinate to the Father. In the beginning of the 4th century, Alexander of Alexandria, and Athanasius, his successor, attempted to unite the hypotheses of Origen and Sabellius, thinking that the truth lay between the two extremes. Athanasius stated the personal distinction of the Father and the Son to be that the former was Without Beginning and Unbegotten, while the latter was Eternally Begotten by the Father, and equally eternal with the Father and the Spirit.
Arius, about 320, disputed the doctrine taught by Alexander, viz. Ἐν Τριάδι Μονάδα Ειναι , and so favored the Sabellian theory. As the controversy proceeded, Arius declared, in opposition to Sabellius, that there were not only three persons in God, but that these were unequal in glory ( Δόξαις Οὐχ Ὅμοιαι ); that the Father alone was supreme God ( Ἀγέννητος ) , and God in a higher sense than the Son; that the Son derived his divinity from the Father before the creation of the world, and that he owed his existence to the divine will; and that the Holy Spirit was likewise divine in a sense inferior to that in which the Father is so. In opposition to all the Arian, and various other theories, Athanasius and his followers zealously contended. They succeeded, at a general council at Nice in 325, in having a symbol adopted which was designed to be thenceforward the only standard of orthodoxy. This symbol was confirmed by the council held at Constantinople in 381, under Theodosius the Great. The distinctions established at Nice and Constantinople were often reenacted at various succeeding councils. Many urged, in opposition, that tritheism (q.v.) was the inevitable consequence of the admission of these distinctions, but they, nevertheless, remained in force. The council adopted the word Ὁμοούσιος (consubstantiality), explaining themselves thus: The Son was not created, but eternally generated from the nature of the Father, and is therefore in all respects equal to him, and no more different, as to nature, from God than a human son is from his father, and so cannot be separated from the Father. All that they meant to teach by the use of this word was that the Father, Son, and Holy Spirit had the divine nature and divine perfections so in common that one did not possess more and another less; without asserting, however, that there were three Gods; in short, that in the Godhead there were Tres Distincti, Unitate Essentice Conjuncti. (See Nicene Creed).
The characteristics by which the persons of the Trinity may be distinguished from each other under this view belong to two classes.
(1.) Internal ( " characteres interni"). These are distinctive signs arising from the internal relation of the three persons in the Godhead to each other, and indicating the mode of the divine existence. The following distinctions are derived from the names Father, Son, and Spirit, and from some other Bible phraseology:
(a.) The Father Generates the Son, and Emits the Holy Spirit, Generat Filium, Spirat Spiritum Sanctum ; and possesses, therefore, as his personal attributes, Generatio Activa and Spiratio Activa.
(b.) The Son is Generated by the Father — Filii Est Generari Non Generare. The Son, therefore, possesses as his personal attributes Jiliatio, Generatio Passiva ; and also, as he is supposed to emit the Spirit in conjunction with the Father, Spiratio Activa.
(c.) The Holy Spirit neither generates nor is generated, but proceeds from the Father and the Son-Spiritus Sanctus Est, Nec Generare Nec Generari, Sed Procedere. In regard to the Holy Spirit, there was nothing decided, during the first three centuries, by ecclesiastical authority respecting his nature, the characteristics of his person, or his relation to the Father and the Son. Nor was anything more definite, with regard to his nature and his relation to the other persons of the Trinity, than what has already been stated, established by the council at Nice, or even by that at Constantinople. To believe in the Holy Ghost — Τὸ Σὺν Πατρὶ Καὶ Υἱῷ Συμπροσκυνούμενον , and Ἐκ Τοῦ Πατρὸς Ἐκπορευόμενον was all that was required in the symbol there adopted. But there were many, especially in the Latin Church, who maintained that the Holy Spirit did not proceed from the Father only, but also from the Son. They appealed to John 16:13, and to the texts where the Holy Spirit is called the Spirit of Christ, e.g. Romans 8:9. To this doctrine the Greeks were, for the most part, opposed, because they did not find that the New Test. ever expressly declared that the Spirit proceeded from the Son. It prevailed, however, more and more in the Latin Church; and when in the 5th and 6th centuries the Arians urged it as an argument against the equality of Christ with the Father, that the Holy Spirit proceeded from the Father only, and not from the Son, the Catholic churches began to hold more decidedly that the Holy Spirit proceeded from both and insert the adjunct Filioque after Patre in the Symbolusm Nicceno-Constantinopolitaium.
(2.) External ("characteres externi"). These are characteristics of the persons of the Trinity arising from the Works of the Deity relating to objects extrinsic to itself, and called opera externa, sive ad extra. They are twofold:
(a.) Opera Dei Aeconomica, those institutions which God has founded for the salvation of the human race. The Father sent his Son to redeem men ( John 3:16-17), and gives or sends the Holy Spirit ( John 14:26). The Son is sent from the Father, etc., and sends the Holy Spirit from the Father ( John 15:26). The Holy Spirit formed the human nature of Christ ( Luke 1:35) and anointed it ( Acts 10:38), i.e. endowed it with gifts; and is sent into the hearts of men, and carries them forward towards moral perfection.
(b.) Opera Dei Attributiva, such divine works as are common to the three persons, but which are frequently ascribed to one of the three. To the Father are ascribed the decree to create the world, the actual creation, and the preservation of it. To the Son, also, the creation, preservation, and government of the world are ascribed; also the raising of the dead and judgment. To the Holy Spirit are ascribed the immediate revelation of the divine will to the prophets, the continuation of the great work of salvation commenced by Christ, and the communication and application to men of the means of grace.
4. History Of The Doctrine Since The Reformation. Nearly all the writers upon the subject of the Trinity since the Reformation belong to some one of the general classes already mentioned. We present several theories.
(1.) Some have attempted to illustrate and explain this doctrine by philosophy; and not a few have gone so far as to think they could prove the Trinity A Priori, and that reason alone furnishes sufficient arguments for its truth. Others, again, looked to reason for nothing more than an illustration of this factor of the divine existence. In the latter class may be placed Philip Melancthon, who, in his Loci Theologici, thus explained the Trinity: "God from his infinite understanding produces thought, which is the image of himself. To this thought he imparted Personal existence, which, bearing the impress of the Father, is his likeness And resemblance: and hence called by John Λόγος . This illustration of the Trinity was received without offence or suspicion, until the heresy, which lurks beneath it was detected and exposed by Flacius. The latest attempt to explain the Trinity in this manner may be found in the Berliner Monatsschrift, Sept. 1790, § 280, in an article written by Schwab of Stuttgart, who refers to the accidents of space, viz. length, breadth, and thickness, as an illustration of the Trinity. Among those who supposed that the Trinity could be mathematically proved were Bartholomew Keckerman, in his Systema Theologicum; Peter Poiret, and Daries, who published an essay In qua Pluralitas Pe'sonaarum in Deitate Methodo Mathematicorum, Demonstratur (Leovardiae, 1735, 8vo).
(2.) Others have expressed themselves so boldly on the subject of the Trinity that they have seemed to approximate towards Tritheism ; in which. class we may mention Matthew Gribaldus of Padua, in the 16th century, who maintained that the divine nature consisted of three equally eternal spirits, between whom, however, he admitted a distinction in respect to rank and perfections.
(3.) Some modern writers have inclined to adopt the Sabellian theory, among whom were Servetus (q.v.), Grotius, Silvae Sacrae ; Stephen Nye, Doctrine Of The Trinity (Lond. 1701). In this class we place the hypothesis of Le Clerc, that the Father, Son, and Holy Spirit designate the different modifications of the divine understanding, and the plans which God forms. This is the error into which Weigel and Jacob Bohme fell. Many of the modern German theologians have so explained the Trinity as to lose the idea of three ‘ divine Persons, for which they have substituted either three distinct Powers Or Attributes (as Meier, Seller, Claudius, and Tollner), or a threefold Agency in God-three eternal actions distinct from each other (as S. G. Schlegel, Kant, Tieftrunk, Daub, Schelling, De Wette, and Fessler).
(4.) The Aian theory has also found advocates among Protestant theologians, especially those of the 18th century (e.g. Whiston, Harwood, and Wettstein); but the system which has met with the most approbation is that more refined subordinationism taught by Samuel Clarke, Scripture Doctrine Of The Trinity (Lond. 1712).
(5.) The Socinians or Photinians. The founders of this sect were Lelius Socinus and his nephew Faustus Socinus (q.v.), who brought over considerable numbers to their doctrine in Poland and Transylvania.
(6.) A new theory on the Trinity was proposed by Dr. Urlsperger, Kurzgefasstes System Seines Vortrags Von Gottes Dreyeinigkeit (Augsburg, 1777, 8vo). He endeavored to unite the three theories — the Arian, Sabellian, and Nicene-by making a distinction between Trinitas Essentialis, the internal threefold distinction necessarily belonging to the divine nature, and Trinitas Aeconomica, the three persons revealed to us in the work of redemption.
It is proper to say that "the conclusion is obvious that, while we are taught by the Scriptures to believe in three equal subjects in the Godhead, who are described as persons, we are still unable to determine in what manner or in what sense these three have the divine nature so in common that there is only one God" (Knapp, Christ. Theology, § 34-44). (See Person).
III. Practical Value Of The Christian Doctrine Of The Trinity. — The idea of a triune being — Father, Son, and Holy Ghost — is not by any means to be considered as separate from that of the nature and attributes of God. This apparent tritheism can be considered as the conclusion of true deism, and as a safeguard in the most momentous questions. Polytheism, pantheism, and dualism have been to some extent employed to vivify and prove the truth of religion; but we would present the practical advantages of the doctrine of the Trinity in quite a different manner; not as serving merely to prove another proposition without being also true in itself, but as aiding us in arriving at the knowledge of God's nature with an efficacy which is essentially inherent to its objective and permanent recognition. God may be considered either as not true or lofty enough, or not good and holy enough, or not essentially active enough; these may be considered the possible faults of a given system of deism. So long, then, as it distinguishes only between God and the world, and not between God himself, it retains always a tendency either to return to pantheism or to deny the existence of an absolute being. An absolute safeguard against atheism, polytheism, pantheism, or dualism cannot be found except in the doctrine of the Trinity; for the distinction existing between the Divine Being and the world is better made and observed as an absolute one by those who worship the triune God than by those who do not. Those monotheistic systems which were the most strenuously opposed to the idea of a Trinity, such as Judaism and Mohammedanism, have, by reason of their dryness and emptiness, led to the grossest pantheism.
From the doctrine that the Word, who was God, became flesh, follows the necessity of considering God as personally united with sinless humanity, but at the same time, also, the necessity of drawing a clear distinction between the divine essence and mere human nature. Faith in the everlasting holy love, which is God, can only be rendered theoretically and practically perfect by the knowledge of the perfect, eternal object of the self- consciousness and love of God; i.e. by the thought of the love of God for his only begotten Son. Finally, the idea of the fullness of God's creative and imparting nature can only be preserved from diminishing by the Trinitarian doctrine of a Holy Ghost. Whatever difficulties may result from the Christian idea of different divine persons, when brought into connection with the personality of the divine essence, the apparent contradiction is yet susceptible of a solution; even when we do not consider that the Primitive Church did not, for a long time, recognize these three persons but as only Ἰδιότητες , Ὑποστάσεις , etc.
The Latin Church alone has, since Augustine, sanctioned the expression personce in the Symbolum Quicunque. Augustine himself said, yet, "Tres personse, si ita dicendae sunt." Some consider the Trinity as essential to constitute the perfect personality, and employ the metaphysics of consciousness as an analogical proof thereof (see Schneider, Colestin, drei geistliche Gesprdche i. d. Personen d. Gottheit , 1). Others refuse to recognize the real personality of God in any but one of the so-called hypostases: namely in the Logos, the Son. Such is Swedenborg. Others still hold peculiar opinions. At any rate, we are obliged, according to the clear sense of Scripture, to seek not only the Trias in the subjectivity of the representation, nor exclusively in the economy of revelation, but also recognize that immediate faith does here contain within itself the germ of endless speculation; not only because every theological system of antiquity, from the time when, as reflecting gnosis, it rose above the myths, shows certain higher theological ideas (in the sense in which Nitzsch has presented it in a historical and critical manner in his Theol. Stud. ch. 1), nor merely because the Christian theologians of all times have made a certain rational understanding of this mystery possible and found it necessary. It is even essentially necessary for the Biblical theologian to recognize in the notion of the Logos-who is with God and is God, the procreative image of God, the inmost spirit of God who knew God-the elements of essential, immanent Trinity. For those only retain the trace of Biblical theology who, in all attempts at explaining it, keep in view the notion of the self- knowledge and self-love of God, or of the distinction between the self- concealing and self-revealing God. Twesten has latterly greatly perfected the philosophy of the doctrine of the Trinity, in its history and in its essence; first by placing the Trinity Κατὰ Τὸν Ἀποκαλύψεως Τρόπον , as subordinate to the analogical and philosophical interpretation; but then, again, Κατὰ Τρόπον Ὑπάρξεως , and shows the connection between both interpretations. In the first case, he seeks a mediation between the Ens Absolutum and the finite world which yet reveals the infinite, and this he finds in the primordial, creative thought of God. But revelation cannot take place except towards discerning beings, and finite beings cannot know God save through God. This argument presents the three notions of God, Logos, and Spirit, yet forming still but one godhead. Such as God reveals himself, such, however, he is. This leads us to another consideration, viz. that the ego, in order to possess a real, living personality, must not only become dually contradistinguished within itself, but also, by a third process, reflectively act on itself as a third subject, and be conscious of itself as being a perfect image of self. This manner of treating this mystery, by analogy, is neither accidental nor gratuitous, since, according to Scripture, human nature is also analogous to the divine. Tertullian and Augustine had themselves established their theories already on this basis.
IV. Literature. — This is immensely copious. We can here refer only to a few leading authorities. See Baur, Hist. Of Doctrines ; Burris, The Trinity (Chicago, 1874); Cunningham, Hist. Theology, 1, 267; Lamson, Origin Of Trinity ; Lessing, Das Christenthum Und Die Vernunft (Berlin, 1784, 8vo); Marheinecke, Grundlehren Der Christl. Dogm. p. 129,370 (ibid. 1819); Mattison, The Trinity And Modern Arianism (18mo); Morus, Commentary ; Mosheim, Leben Servet'S (Helmst. 1748, 8vo); Meier, Historical Development Of The Trinity ; Neander, 2, 2, 891; Sailer, Theorie Des Weisen (Spottes, 1781, 8vo); Walch, Historia Controversice Graecorum Latinorumque De Processione Spiritus Sancti (Jenae, 1751, 8vo); Ziegler, Geschichtsentwickelung Des Dogma Vom Heiligen Geist. For further literature see Biblioth. Sac. (184473), index to vol. 1-30; Dantz, W Ö rterbuch der theol. Literatur, s.v. "Trinitit;" Darling, Cyclop. Bibliog. col. 268, 1446, 1719-1722; Poole, Index to Period. Lit. s.v. "Trinity."
The Nuttall Encyclopedia 
The doctrine, variously interpreted, that in the godhead or divine nature there are three persons, respectively denominated Father, Son, and Spirit—Father, from whom; Son, to whom; and Spirit, through whom are all things; is essentially triunity in unity.
- Trinity from Watson's Biblical & Theological Dictionary
- Trinity from Hastings' Dictionary of the Bible
- Trinity from Bridgeway Bible Dictionary
- Trinity from Holman Bible Dictionary
- Trinity from Charles Buck Theological Dictionary
- Trinity from Morrish Bible Dictionary
- Trinity from People's Dictionary of the Bible
- Trinity from Webster's Dictionary
- Trinity from Easton's Bible Dictionary
- Trinity from Hastings' Dictionary of the New Testament
- Trinity from International Standard Bible Encyclopedia
- Trinity from Cyclopedia of Biblical, Theological and Ecclesiastical Literature
- Trinity from The Nuttall Encyclopedia