2. _Technical Forms of the Platonists._--The other sects of the Greek philosophy, as well as the Aristotelians, invented and adopted technical terms, and thus gave fixity to their tenets and consistency to their traditionary systems; of these I will mention a few. A technical expression of a contemporary school has acquired perhaps greater celebrity than any of the terms of Aristotle. I mean the _Ideas_ of Plato. The account which Aristotle gives of the origin of these will serve to explain their nature.[37\1] "Plato," says he, "who, in his youth, was in habits of communication first with Cratylus and the Heraclitean opinions, which represent all the objects of sense as being in a perpetual flux, so that concerning these no science nor certain {76} knowledge can exist, entertained the same opinions at a later period also. When, afterwards, Socrates treated of moral subjects, and gave no attention to physics, but, in the subjects which he did discuss, arrived at universal truths, and before any man, turned his thoughts to definitions, Plato adopted similar doctrines on this subject also; and construed them in this way, that these truths and definitions must be applicable to something else, and not to sensible things: for it was impossible, he conceived, that there should be a general common definition of any sensible object, since such were always in a state of change. The things, then, which were the subjects of universal truths he called _Ideas_; and held that objects of sense had their names according to Ideas and after them; so that things participated in that Idea which had the same name as was applied to them." [Note 37\1: Arist. Metaph. i. 6. The same account is repeated, and the subject discussed, Metaph. xii. 4.] In agreement with this, we find the opinions suggested in the _Parmenides_ of Plato, the dialogue which is considered by many to contain the most decided exposition of the doctrine of Ideas. In this dialogue, Parmenides is made to say to Socrates, then a young man,[38\1] "O Socrates, philosophy has not yet claimed you for her own, as, in my judgment, she will claim you, and you will not dishonor her. As yet, like a young man as you are, you look to the opinions of men. But tell me this: it appears to you, as you say, that there are certain _Kinds_ or _Ideas_ (εἰδὴ) of which things partake and receive applications according to that of which they partake: thus those things which partake of _Likeness_ are called _like_; those things which partake of _Greatness_ are called _great_; those things which partake of _Beauty_ and _Justice_ are called _beautiful_ and _just_." To this Socrates assents. And in another part of the dialogue he shows that these Ideas are not included in our common knowledge, from whence he infers that they are objects of the Divine mind. [Note 38\1: Parmenid. p. 131.]