Then again, Parmenides--and those who affirm that Ens Totum was essentially Unum, denying all plurality--had difficulties on their side to surmount. Ens could not be identical with Unum, nor was the name _Ens_, identical with the thing named Ens. Moreover, though Ens Unum was _Totum_, yet Totum was not identical with Ens or with Unum. _Totum_ necessarily implied _partes_: but the _Unum per se_ was indivisible or implied absence of parts. Though it was true therefore that Ens was both Unum and Totum, these two were both of them essentially different from Ens, and belonged to it only by way of adjunct accident. Parmenides was therefore wrong in saying that Unum alone existed. [Side-note: Plato's refutation throws light upon the doctrine of Antisthenes.] The reasoning here given from Plato throws some light upon the doctrine just now cited from Antisthenes. You cannot say (argues Plato against the advocates of duality) that _two_ elements (Hot and Cold) are both of them Entia or Existent, because by so doing you call them _one_. You cannot say (argues Antisthenes) that Sokrates is good, brave, old, &c., because by such speech you call one thing three. Again, in controverting the doctrine of Parmenides, Plato urges, That Ens cannot _be_ Unum, because it is Totum (Unum having no parts, while Totum has parts): but it may carry with it the accident Unum, or may have Unum applied to it as a predicate by accident. Here again, we have difficulties similar to those which perplexed Antisthenes. For the same reason that Plato will not admit, That Ens _is_ Unum--Antisthenes will not admit, That Man _is_ good. It appeared to him to imply essential identity between the predicate and the subject. All these difficulties and others to which we shall come presently, noway peculiar to Antisthenes--attest the incomplete formal logic of the time: the want of a good theory respecting predication and the function of the copula. [Side-note: Plato's argument against the Materialists.] Pursuing the purpose of establishing his conclusion (_viz._ That Ens involved as many perplexities as Non-Ens), Plato comes to the two opposite sects:--1. Those (the Materialists) who recognised bodies and nothing else, as the real Entia or Existences. 2. Those (the Friends of Forms, the Idealists) who maintained that incorporeal and intelligible Forms or Species were the only real existences; and that bodies had no existence, but were in perpetual generation and destruction.[102] [Footnote 102: Plato, Sophist. p. 246 B.]