Charles Buck Theological Dictionary 
Signifies that science which treats of the being and attributes of God, his relations to us, the dispensations of his providence, his will with respect to our actions, and his purposes with respect to our end. The word was first used to denote the systems, or rather the heterogeneous fables, of those poets and philosophers who wrote of the genealogy and exploits of the gods of Greece. Hence Orpheus, Museus, Hesiod, &c. were called theologians; and the same epithet was given to Plato, on account of his sublime speculations on the same subject. It was afterwards adopted by the earliest writers of the Christian Church, who styled the author of the Apocalypse, by way of eminence, the divine. As the various branches of theology are considered in their places in this work, they need not be insisted on here. The theological student will find the following books on the subject of utility; Gratius de Veritate Religionis Christianae; Stillingfleet's Origines Sacrae; Turretine's Institutio Theologiae Elencticae; Butler's analogy; Picteti Theologia Christiana; Stupferi Institutiones Theologiae; Witsius on the Covenants; Usher, Boston, Watson, Gill, and Ridgley's Divinity; Doddridge's Lectures; Brown's compendium of Natural and Revealed Religion; and Ryan's Effects of Religion on Mankind.
See also articles Christianity, Religion, Revelation, Scriptures
Webster's Dictionary 
(n.) The science of God or of religion; the science which treats of the existence, character, and attributes of God, his laws and government, the doctrines we are to believe, and the duties we are to practice; divinity; (as more commonly understood) "the knowledge derivable from the Scriptures, the systematic exhibition of revealed truth, the science of Christian faith and life."
Cyclopedia of Biblical, Theological and Ecclesiastical Literature 
(from Θεός , God, and Λόγος , discourse) . is not to be interpreted simply as its etymology requires, as The Doctrine Of God, nor yet historically, as the doctrine of the Trinity, but is to be understood with reference to a definite range of life which it is to bring into the consciousness and apprehend both theoretically and practically. Theology is not, consequently, the doctrine of the Christian religion, nor of the self-consciousness of God in man, as speculative theology is wont to speak, nor yet of the feeling of the Absolute. It is primarily the shaping of a life in man; in the language of Steenstrup, the Danish divine, it is an internal habit, which lies deeper than the intellect. This has been conceded since the time of Schleiermacher with reference to both religion and theology. Rudelbach describes it as a science of divine things mediated by the Spirit of God. Vilmar teaches that true theology is esoteric in form, because truly scientific; but also practical, because it involves piety and the entire contents of religion. It sustains to the practical life; however, only the relation of idea to practice. The heart of the Christian life is, moreover, not religion, but the kingdom of God, or God's organic revelation to the world-the Church (see Storr, Schleiermacher, Baumgarten-Crusius, and many Romish theologians; also Kling, in Herzog, Real-Encyklop. 12:600-606). Theology thus becomes the science of the unfolded, objective self-manifestation of the Divine Spirit in the phenomenal kingdom of God a practical science which develops progressively and side by side with that kingdom. But it is nonetheless a positive science also through its relation to the kingdom. Schleiermacher (Kurze Darstell. etc.) describes Christian theology as the comprehension of all that scientific knowledge and those scientific methods without whose possession and use a harmonious direction of the Christian Church, i.e. a Christian Church government is not possible. This definition is, however, too external; for in the material of theology all truth finds its goal, and that fact should be expressed in its definition. Both the object and the scientific character of theology will be retained if the latter be defined as the scientific self-consciousness of the Church with reference to its development through the Holy Spirit, or, more briefly, its self- consciousness with respect to its self-edification.
From this definition theology branches out into particular departments. The self-consciousness has for its first task the apprehension of the Church in actuality by determining its historical origin, development, and present state. Historical theology is the history of the kingdom of God consciously apprehended. It subdivides into the three special branches of Sacred History, Ecclesiastical History, and Ecclesiastical Statistics.
The determination of sources and portrayal of the outworking and development of the leading principles by which events are governed are of primary importance in historical study. The first source here is wholly unique, being the might of the Divine Spirit. The source for the beginnings of the Christian Church is, at the same time, a regulative guide and vivifying principle to the Church. By the side of other sources it affords knowledge respecting the time of the origin of the Old Covenant, and its development until it became the New, and it possesses unquestionable authority as the earliest witness to the operative power of the Divine Spirit in the world, and consequently as its mediating principle, or as the Bible, the only sacred book.
The first part of historical theology is consequently a knowledge respecting the Bible (Biblical theology, in the wider meaning). It is all-important to determine what books belong to the Bible, and this is the business of the Canon. The whole Bible is to be authenticated both in its parts and its text; to accomplish this is the work of historical and textual criticism. Introduction to the books of the Old and New Tests. (Isagogics), or, more exactly, the History of the Canon and of Biblical Literature, presents the collective material to view, and is followed by philological and theological exposition. The scientific conception of this expository work is Hermeneutics, or the art of interpretation. The history of the Word of God, the Divine Revelation, and the presentation of its contents which have attained to their development are given in Sacred History (and Archaeology) and in Biblical Dogmatics and Ethics-usually termed, in Germany, Biblical Theology of the Old and New Tests.; the latter being the final and gradually developing phase of the Divine Revelation, whose central point is the establishing of the kingdom of divine grace through Jesus Christ. This science is theologico-historical, and therefore deals largely with details, e.g. the particular doctrinal contents of separate Old- Test. books, etc.
Personal convictions are of great importance in this connection. Without being rooted in the Divine Revelation, no apprehension of its meaning is possible. The contents of the Revelation as appropriated both by the individual and the Church must accordingly be received into the scientific consciousness, which indicates the task of scientific theology. The latter, however, does not derive its contents directly from the Bible, but through numerous intermediate agencies, to contemplate which is the work of Ecclesiastical History, and, in so far as they belong to the present age of the Church, of Ecclesiastical Statistics.
Ecclesiastical History portrays the history of the kingdom of God in time from the founding of the Christian Church on the day of Pentecost to the present day, having the end of prophecy continually in view as its goal. It directs its attention more prominently either to the outward development of that kingdom in the Church and the life as renewed and inspired by Christianity (Church History), or to the consciousness of that development and its contents the History of Doctrines and the connected History of Christian Ethics, Literature, and Art. The study of Sources, Geography, Chronology, etc., likewise involves much that is peculiar, and requires the separate theological treatment of those branches, in consequence of which originate Patristics, Ecclesiastical Archaeology, History of Liturgies, etc.
The present not only forms the limit of development at which the kingdom of God has arrived, but also the ground on which we stand. The description of this ground is the work of Ecclesiastical Statistics. It includes both external and internal conditions, both of the faith and the life, and gives rise, on the one hand, to Statistics of Churches in different countries and of different denominations and sects, and, on the other, to Historical Symbolics.
Inquiry into, the faith and morals of different denominations leads from Statistics over to Systematic Theology. The nature of the latter is determined by the nature of the Christian consciousness as based on a new life in the individual and the race. The development of that consciousness into scientific knowledge requires, first, an assured recognition of the principles which underlie the kingdom of God as manifested in Christianity; next, an unfolding of the contents of such principles in systematic form; and, finally, a recognition of the relation of this knowledge to the universe of human knowledge. In this way is obtained a science of the principles and the particular phenomena of Christianity as they are given in its history (the science of Christian principles or fundamentals), a science of their doctrinal and ethical contents generally, and also in the particular confessions (thetical theology), and a philosophy of Christianity (parallel to the philosophy of law in a different field of ethics).
As Systematic Theology does not proceed from the Christian convictions of the individual, but from those of the entire Church or of one of its subordinate parts, it provides room for Ecclesiastical Tradition. The starting-point is the idea of the kingdom of God which rests on the Word of God as objectively presented to us in the Canon, as approved in the heart in the character of Christ, and as given in Tradition in the forms of faith, custom, constitution, and methods. The consummation is in the Dogma, in which God's kingdom is the object of the scientific consciousness of the general Church, or, under historical limitations, assumes a definite form in the particular denomination (Denominational Principles or Systematic Symbolics). At this point the doctrinal consciousness discovers its variation from the systems of other denominations and of morbid apparitions within the Church to which it belongs. The latter observation gives rise to Polemics, or, better, the Discussion of ethical and doctrinal excrescences in the Church (analogous to pathology in medicine).
The ground has thus been prepared for the founding and establishing of Thetical Theology, the confessional Dogmatics and Ethics as traditionally determined on the basis of the underlying faith. Here the dogma, in its character of scriptural truth subjectively apprehended and handed down in the Church by authoritative tradition, attains to its complete development; and here the various doctrines are combined into a system through the labors of critical, religiously ethical, and systematic scholars. The true relation is accurately indicated by the oxymoron in the phrase "the science of the faith." Unquestionable certainty is given in the faith, but the mind transmutes this successively and partially into knowledge.
This dogmatico-ethical process begets a system of knowledge respecting God and divine things. This constitutes Speculative Theology, the last result of a philosophy of Christianity which was conceived in mysticism, unfolded in theosophy, sifted by criticism, and formed by speculation, and now presents Christianity with the science of it as the center and goal of all culture and as the crown of the scientific labors of the entire human race. Christianity is here presented as a religion, and as the highest manifestation of religion, and also as the complete realization of the kingdom of God on earth through a progressive development, which reaches down to the final consummation; and in this light Christianity is presented as the central feature in the philosophy of human history.
The duty of the Church to insure its own edification through the power of the Holy Spirit comes into prominence here, as it does in the historical department. That edification is Ecclesiastical Praxis, and the scientific understanding of its foundations and methods constitutes Practical Theology, the third principal branch of theological science. The starting- point of this science is the energy of the Christian life, which is to be perfected. Practical theology is the science of human operations within the kingdom of God and as enabled by the Holy Spirit, to the end that that kingdom may be fully developed. Only through God can we arrive at God, in knowledge as in feeling or in practice.
The setting forth of these fundamentals, and of the methods by which the organism of God's kingdom, particularly in the Church, is to be erected on them, is the work of the science of Ecclesiastical Foundations, otherwise the science of the principles of Practical Theology, which finds its completion in the science of Church organization. We next discover a separate department of Church law, which constitutes the second part of Practical Theology, and subdivides into Church law and Church government (in a restricted sense, Church polity; in an unrestricted, the care of souls). The process of self-edification under the Holy Spirit's influence, moreover, gives rise to a recognition of the means through which this is achieved, and thereby originated a third technical part. covering the theories of art methods in the different Christian churches, which are known, with reference to the shaping of the external forms of worship so that they may represent the worship of the inner man, as Liturgics; with reference to the proclamation of the Word of God, as Homiletics or Keryktics; with reference to the training of the young, as Christian Pedagogics and Catechetics; with reference to the conversion of heathen and other false religionists, as Halieutics and Theory of Missions, and with reference to the organization of scientific instruction for the Church, as Ecclesiastical Paedeutics, which has to do with the Christian organization of institutions of learning, as the placing of theological faculties in universities, the founding of theological seminaries, etc. Theological literature cannot, of course, be brought within any rule, but may be classified in conformity with its manner of entering upon the arena of the Christian and the Church life. — Herzog, Real-Encyklop. s.v. (See Theologian).
See Pelt, Theol. Encyklop. (Hamb. and Gotha, 1843), with whose theory the above article is substantially agreed. (See Encyclopedia Of Theology), with the literature there referred to.
International Standard Bible Encyclopedia 
The Nuttall Encyclopedia 
The science which treats of God, particularly as He manifests Himself in His relation to man in nature, reason, or revelation.