The Complete Aristotle (eng.)

accurate arguments, some lead to Ideas of
relations, of which they say there is no independent class, and
others introduce the ‘third man’.
    And in general the arguments for the Forms destroy things for
whose existence the believers in Forms are more zealous than for
the existence of the Ideas; for it follows that not the dyad but
number is first, and that prior to number is the relative, and that
this is prior to the absolute-besides all the other points on which
certain people, by following out the opinions held about the Forms,
came into conflict with the principles of the theory.
    Again, according to the assumption on the belief in the Ideas
rests, there will be Forms not only of substances but also of many
other things; for the concept is single not only in the case of
substances, but also in that of non-substances, and there are
sciences of other things than substance; and a thousand other such
difficulties confront them. But according to the necessities of the
case and the opinions about the Forms, if they can be shared in
there must be Ideas of substances only. For they are not shared in
incidentally, but each Form must be shared in as something not
predicated of a subject. (By ‘being shared in incidentally’ I mean
that if a thing shares in ‘double itself’, it shares also in
‘eternal’, but incidentally; for ‘the double’ happens to be
eternal.) Therefore the Forms will be substance. But the same names
indicate substance in this and in the ideal world (or what will be
the meaning of saying that there is something apart from the
particulars-the one over many?). And if the Ideas and the things
that share in them have the same form, there will be something
common: for why should ‘2’ be one and the same in the perishable
2’s, or in the 2’s which are many but eternal, and not the same in
the ‘2 itself’ as in the individual 2? But if they have not the
same form, they will have only the name in common, and it is as if
one were to call both Callias and a piece of wood a ‘man’, without
observing any community between them.
    But if we are to suppose that in other respects the common
definitions apply to the Forms, e.g. that ‘plane figure’ and the
other parts of the definition apply to the circle itself, but ‘what
really is’ has to be added, we must inquire whether this is not
absolutely meaningless. For to what is this to be added? To
‘centre’ or to ‘plane’ or to all the parts of the definition? For
all the elements in the essence are Ideas, e.g. ‘animal’ and
‘two-footed’. Further, there must be some Ideal answering to
‘plane’ above, some nature which will be present in all the Forms
as their genus.
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5
    Above all one might discuss the question what in the world the
Forms contribute to sensible things, either to those that are
eternal or to those that come into being and cease to be; for they
cause neither movement nor any change in them. But again they help
in no wise either towards the knowledge of other things (for they
are not even the substance of these, else they would have been in
them), or towards their being, if they are not in the individuals
which share in them; though if they were, they might be thought to
be causes, as white causes whiteness in a white object by entering
into its composition. But this argument, which was used first by
Anaxagoras, and later by Eudoxus in his discussion of difficulties
and by certain others, is very easily upset; for it is easy to
collect many and insuperable objections to such a view.
    But, further, all other things cannot come from the Forms in any
of the usual senses of ‘from’. And to say that they are patterns
and the other things share in them is to use empty words and
poetical metaphors. For what is it that works, looking to the
Ideas? And any thing can both be and come into being without being
copied from something else, so that, whether Socrates exists or
not, a man like Socrates might come to be. And evidently this might
be so even if Socrates were eternal. And there will be several
patterns of the same thing, and therefore several Forms; e.g.
‘animal’ and ‘two-footed’, and also ‘man-himself’, will be Forms of
man. Again, the Forms are patterns not only of sensible things, but
of Forms themselves also; i.e. the genus is the pattern of the
various forms-of-a-genus; therefore the same thing will be pattern
and copy.
    Again, it would seem