The other criticism of Parmenides on Socrates attributes to him a want
of practice in dialectic. He has observed this deficiency in him when
talking to Aristoteles on a previous occasion. Plato seems to imply
that there was something more in the dialectic of Zeno than in the mere
interrogation of Socrates. Here, again, he may perhaps be describing
the process which his own mind went through when he first became more
intimately acquainted, whether at Megara or elsewhere, with the Eleatic
and Megarian philosophers. Still, Parmenides does not deny to Socrates
the credit of having gone beyond them in seeking to apply the paradoxes
of Zeno to ideas; and this is the application which he himself makes of
them in the latter part of the dialogue. He then proceeds to explain
to him the sort of mental gymnastic which he should practise. He should
consider not only what would follow from a given hypothesis, but what
would follow from the denial of it, to that which is the subject of
the hypothesis, and to all other things. There is no trace in the
Memorabilia of Xenophon of any such method being attributed to
Socrates; nor is the dialectic here spoken of that 'favourite method' of
proceeding by regular divisions, which is described in the Phaedrus and
Philebus, and of which examples are given in the Politicus and in the
Sophist. It is expressly spoken of as the method which Socrates had
heard Zeno practise in the days of his youth (compare Soph.).
The discussion of Socrates with Parmenides is one of the most remarkable
passages in Plato. Few writers have ever been able to anticipate 'the
criticism of the morrow' on their favourite notions. But Plato may here
be said to anticipate the judgment not only of the morrow, but of
all after-ages on the Platonic Ideas. For in some points he touches
questions which have not yet received their solution in modern
philosophy.
The first difficulty which Parmenides raises respecting the Platonic
ideas relates to the manner in which individuals are connected with
them. Do they participate in the ideas, or do they merely resemble them?
Parmenides shows that objections may be urged against either of these
modes of conceiving the connection. Things are little by partaking of
littleness, great by partaking of greatness, and the like. But they
cannot partake of a part of greatness, for that will not make them
great, etc.; nor can each object monopolise the whole. The only answer
to this is, that 'partaking' is a figure of speech, really corresponding
to the processes which a later logic designates by the terms
'abstraction' and 'generalization.' When we have described accurately
the methods or forms which the mind employs, we cannot further criticize
them; at least we can only criticize them with reference to their
fitness as instruments of thought to express facts.