By this, according to Sir William Hamilton, " is understood the mere possession of truths," and the possession of those truths about which our faculties have been previously employed, rather than any separate power of the understanding by which truth is perceived. " I know no authority," says Dr. Reid, "besides that of Mr. Locke. for calling knowledge a faculty, any more than for calling opinion a faculty." Knowledge is of two kinds, viz. historical or empirical, and philosophical, or scientific or rational. Historical is the knowledge that the thing is, philosophical is the knowledge why or how it is. The first is called historical, because in this knowledge we know only the fact — only that that phenomenon is; for history is properly only the narration of a consecutive series of phenomena in time, or the description of a co-existent series of phenomena in space; the second philosophical, to imply that there is a way of knowing things more completely than they are known through simple experiences mechanically accumulated in memory or heaped up in cyclopaedias. It seeks for wide and deep truths, as distinguished from the multitudinous detailed truths which the surface of things and actions presents, and therefore a knowledge of the highest degree of generality. " The truth of philosophy," says Herbert Spencer, bears the same relation to the highest scientific truths that each of these bears to lower scientific truths. As each widest generalization of science comprehends and consolidates the narrower generalizations of its own division, so the generalizations of philosophy comprehend and consolidate the widest generalizations of science. It is therefore a knowledge the extreme opposite in kind to that which experience first accumulates. It is the final product of that process which begins with a mere colligation of crude observations, goes on establishing propositions that are broader and more separated from particular cases, and ends in universal propositions. Or, to bring the definition to its simplest and clearest form, knowledge of the lowest kind is ununified knowledge; science is partially unified knowledge; philosophy is completely unified knowledge."
This term, however, is associated with the greatest problems and controversies of philosophy, all of which are involved in the discussion of what is meant by knowledge. The different problems, therefore, of the philosophy of mind will be found discussed under those names that severally suggest them. — Watts, On the Mind; Dr. John Edwards, Uncertainty, Deficiency, and Corruption of Human Knowledge; Reid, Intellectual Powers of Man; Stennett, Sermon on Acts t 16:24, 25: Upham, Intellectual Philosophy; Douglas, On the Advancement of Society; Robert Hall, Works; Amer. Library of Useful Knowledge. (See Faith And Reason); (See Idealism); (See Judgment); (See Moral Philosophy); (See Religious Philosophy).