This investigation is resumed in the "Republic." This greatest work of Plato's was designed not only to exhibit a scheme of Polity, and present a system of Ethics, but also, at least in its digressions, to propound a system of Metaphysics more complete and solid than had yet appeared. The discussion as to the powers or faculties by which we obtain knowledge, the method or process by which real knowledge is attained, and the ultimate objects or ontological grounds of all real knowledge, commences at § 18, book v., and extends to the end of book vii.
That we may reach a comprehensive view of this "sublimest of sciences," we shall find it necessary to consider--
1st. What are the powers or faculties by which we obtain knowledge, and what are the limits and degrees of human knowledge?
2d. What is the method in which, or the processes and laws according to which, the mind operates in obtaining knowledge?
3d. What are the ultimate results attained by this method? what are the objective and ontological grounds of all real knowledge?
The answer to the first question will give the PLATONIC PSYCHOLOGY; the answer to the second will exhibit the PLATONIC DIALECTIC; the answer to the last will reveal the PLATONIC ONTOLOGY.
I. PLATONIC PSYCHOLOGY.
Every successful inquiry as to the reality and validity of human knowledge must commence by clearly determining, by rigid analysis, what are the actual phenomena presented in consciousness, what are the powers or faculties supposed by these phenomena, and what reliance are we to place upon the testimony of these faculties? And, especially, if it be asserted that there is a science of absolute Reality, of ultimate and essential Being, then the most important and vital question is, By what power do we cognize real Being? through what faculty do we obtain the knowledge of that which absolutely is? If by sensation we only obtain the knowledge of the fleeting and the transitory, "the becoming" how do we attain to the knowledge of the unchangeable and permanent, "the Being?" Have we a faculty of universal, necessary, and eternal principles? Have we a faculty, an interior eye which beholds "the intelligible," ideal, spiritual world, as the eye of sense beholds the visible or "sensible world?" [521]
Plato commences this inquiry by first defining his understanding of the word δύναµις--power or faculty. "We will say faculties (δυνάµεις) are a certain kind of real existences by which we can do whatever we are able (e.g., to know), as there are powers by which every thing does what it does: the eye has a power of seeing; the ear has a power of hearing. But these powers (of which I now speak) have no color or figure to which I can so refer that I can distinguish one power from another. In order to make such distinction, I must look at the power itself, and see what it is, and what it does. In that way I discern the power of each thing, and that is the same power which produces the same effect, and that is a different power which produces a different effect." [522] That which is employed about, and accomplishes one and the same purpose, this Plato calls a faculty.
[Footnote 521: ][ (return) ] "Republic," bk. vi. ch. xviii.