Let us turn for a moment (he says) from Non-Ens to Ens. The various physical philosophers tell us a good deal about Ens. They differ greatly among themselves. Some philosophers represent Ens as triple, comprising three distinct elements, sometimes in harmony, sometimes at variance with each other. Others tell us that it is double — wet and dry — or hot and cold. A third sect, especially Xenophanes and Parmenides, pronounce it to be essentially One. Herakleitus blends together the different theories, affirming that Ens is both many and one, always in process of disjunction and conjunction: Empedokles adopts a similar view, only dropping the always, and declaring the process of disjunction to alternate with that of conjunction, so that Ens is sometimes Many, sometimes One.[39]
[39] Plato, Sophist. p. 242 D-E.
Difficulties about Ens are as great as those about Non-Ens.
Now when I look at these various theories (continues the Eleate), I find that I do not follow or understand them; and that I know nothing more or better about Ens than about Non-Ens. I thought, as a young man, that I understood both: but I now find that I understand neither.[40] The difficulties about Ens are just as great as those about Non-Ens. What do these philosophers mean by saying that Ens is double or triple? that there are two distinct existing elements — Hot and Cold — or three? What do you mean by saying that Hot and Cold exist? Is existence any thing distinct from Hot and Cold? If so, then there are three elements in all, not two. Do you mean that existence is something belonging to both and affirmed of both? Then you pronounce both to be One: and Ens, instead of being double, will be at the bottom only One.
[40] Plato, Sophist. p. 243 B.
Whether Ens is Many or One? If Many, how Many? Difficulties about One and the Whole. Theorists about Ens cannot solve them.
Such are the questions which the Eleatic spokesman of Plato puts to those philosophers who affirm Ens to be plural: He turns next to those who affirm Ens to be singular, or Unum. Do you mean that Unum is identical with Ens — and are they only two names for the same One and only thing? There cannot be two distinct names belonging to one and the same thing: and yet, if this be not so, one of the names must be the name of nothing. At any rate, if there be only one name and one thing, still the name itself is different from the thing — so that duality must still be recognised. Or if you take the name as identical with the One thing, it will either be the name of nothing, or the name of a name.[41]
[41] Plato, Sophist. p. 244 D.
Again, as to the Whole:— is the Whole the same with the Ens Unum, or different from it. We shall be told that it is the same: but according to the description given by Parmenides, the whole is spherical, thus having a centre and circumference, and of course having parts. Now a whole divisible into parts may have unity predicable of it, as an affection or accident in respect to the sum of its parts: but it cannot be the genuine, essential, self-existent, One, which does not admit of parts or division. If Ens be One by accident, it is not identical with One, and we thus have two existent things: and if Ens be not really and essentially the Whole, while nevertheless the Whole exists — Ens must fall short of or be less than itself, and must to this extent be Non-Ens: besides that Ens, and Totum, being by nature distinct, we have more things than One existing. On the other hand, if we assume Totum not to be Ens, the same result will ensue. Ens will still be something less than itself; — Ens can never have any quantity, for each quantum is necessarily a whole in itself — and Ens can never be generated, since everything generated is also necessarily a whole.[42]
[42] Plato, Sophist. p. 245 A-C.