Aristotle, Metaphysics

[1079b] [1] and not in the case of absolute duality and a particular 2?). But if the form is not the same, they will simply be homonyms; just as though one were to call both Callias and a piece of wood "man," without remarking any property common to them.

¹And if we profess that in all other respects the common definitions apply to the Forms, e.g. that "plane figure" and the other parts of the definition apply to the Ideal circle, only that we must also state of what the Form is a Form, we must beware lest this is a quite meaningless statement.² For to what element of the definition must the addition be made? to "center," or "plane" or all of them? For all the elements in the essence of an Idea are Ideas; e.g. "animal" and "two-footed."³ Further, it is obvious that "being an Idea," just like "plane," must be a definite characteristic which belongs as genus to all its species.⁴

⁵Above all we might examine the question what on earth the Ideas contribute to sensible things, whether eternal or subject to generation and decay; for they are not the cause of any motion or change in them.Moreover they are no help towards the knowledge of other things (for they are not the substance of particulars, otherwise they would be in particulars) or to their existence (since they are not present in the things which participate in them. If they were, they might perhaps seem to be causes, in the sense in which the admixture of white causes a thing to be white. [20] But this theory, which was stated first by Anaxagoras and later by Eudoxus in his discussion of difficulties, and by others also, is very readily refuted; for it is easy to adduce plenty of impossibilities against such a view). Again, other things are not in any accepted sense derived from the Forms.To say that the Forms are patterns, and that other things participate in them, is to use empty phrases and poetical metaphors; for what is it that fashions things on the model of the Ideas? Besides, anything may both be and come to be without being imitated from something else; thus a man may become like Socrates whether Socrates exists or not,and even if Socrates were eternal, clearly the case would be the same. Also there will be several "patterns" (and therefore Forms) of the same thing; e.g., "animal" and "two-footed" will be patterns of "man," and so too will the Idea of man.Further, the Forms will be patterns not only of sensible things but of Ideas; e.g. the genus will be the pattern of its species; hence the same thing will be pattern and copy. Further, it would seem impossible for the substance and that of which it is the substance to exist in separation;