Timaeus

self-existent, intelligible essence. Plato therefore hypostatizes elevates to the status of a real being the Socratic concept, declaring that every such concept is but our mental adumbration outline or shadow of an eternal and immutable idea. Thus, in every class of material things we have an idea, of which the particulars are the material images, and the concept we form from observing these particulars is our mental image of it. Immaterial essence then exists in the mode of eternal ideas or forms, one of which corresponds to every class—not only of concrete things but of attributes and relations—in fact, to all things that we call by the same class-name (Republic 596 A). The particulars exist, so far as they can be said to exist, through the inherence of the ideas in them—at least this is the way Plato usually puts it, though in Phaedo 100 D he declines to commit himself to a definition of the relation. These ideas are arranged in an ascending scale: lowest, we have the ideas of concrete things; next, those of abstract qualities; and finally, the supreme Idea of the Good, which is the cause of existence to all the other ideas and, hence, to material nature as well.

Now, since there is an idea corresponding to every group of particulars, we may note the following classes of ideas in the theory of the Republic: (1) the idea of the good; (2) ideas of qualities akin to the good, such as the noble (καλόν), the just (δίκαιον), and the like; (3) ideas of natural objects, such as man or horse; (4) ideas of manufactured objects (σκευαστά), such as beds or tables; (5) ideas of relations, such as equal or like; (6) ideas of qualities antagonistic to the good, such as the unjust (ἄδικον), the base (αἰσχρόν), and so forth (Republic 476 A).

Thus, we have a multitude of particulars falling under the above six classes, deriving their existence from a number of causative immaterial essences, which in turn derive their own existence from one supreme essence: the idea of the good. The particulars themselves cannot be known because they have no abiding existence; but by observation and classification of these particulars, we may ascend from concept to concept until we attain the apprehension of the Good itself (αὐτὸ ἀγαθόν), whence we pass to the cognition of the other ideas. Thus, Plato offers a theory of knowledge that enables us to escape metaphysical skepticism. He also offers, in the theory of ideas, a solution to a pressing logical difficulty raised by Antisthenes and others: the possibility of predication. The application of the ideal theory to this question is found in Phaedo 102 B. Predication signifies that the idea of the quality predicated is

Predication.