Now motion is altogether different from rest Motion therefore is not rest. Yet still motion is, because it partakes of existence or Ens. Accordingly, motion both is and is not.
Again, motion is different from Idem or the Same. It is therefore not the same. Yet still motion is the same; because every thing partakes of identity, or is the same with itself. Motion therefore both is the same and is not the same. We must not scruple to advance both these propositions. Each of them stands on its own separate ground.[116] So also motion is different from Diversum or The Different; in other words, it is not different, yet still it is different. And, lastly, motion is different from Ens, in other words, it is not Ens, or is non-Ens: yet still it is Ens, because it partakes of existence. Hence motion is both Ens, and Non-Ens.
[116] Plato, Sophist. pp. 255-256.
Here we arrive at Plato’s explanation of Non-Ens, τὸ μὴ ὂν: the main problem which he is now setting to himself. Non-Ens is equivalent to, different from Ens. It is the Form or Idea of Diversum, considered in reference to Ens. Every thing is Ens, or partakes of entity, or existence. Every thing also is different from Ens, or partakes of difference in relation to Ens: it is thus Non-Ens. Every thing therefore is at the same time both Ens, and Non-Ens. Nay, Ens itself, inasmuch as it is different from all other things, is Non-Ens in reference to them. It is Ens only as one, in reference to itself: but it is Non-Ens an infinite number of times, in reference to all other things.[117]
[117] Plato, Sophist. pp. 256-257.
Plato’s doctrine — That Non-Ens is nothing more than different from Ens.
When we say Non-Ens, therefore (continues Plato), we do not mean any thing contrary to Ens, but merely something different from Ens. When we say Not-great, we nothing do not mean any thing contrary to Great, but only something different from great. The negative generally, when annexed to any name, does not designate any thing contrary to what is meant by that name, but something different from it. The general nature or Form of difference is disseminated into a multitude of different parts or varieties according to the number of different things with which it is brought into communion: Not-great, Not-just, &c., are specific varieties of this general nature, and are just as much realities as great, just. And thus Non-Ens is just as much a reality as Ens being not contrary, but only that variety of the general nature of difference which corresponds to Ens. Non-Ens, Not-great, Not-just, &c., are each of them permanent Forms, among the many other Forms or Entia, having each a true and distinct nature of its own.[118]
[118] Plato, Sophist. p. 258 C. ὅτι τὸ μὴ ὂν βεβαίως ἐστὶ τὴν αὐτοῦ φύσιν ἔχον … οὕτω δὲ καὶ τὸ μὴ ὂν κατὰ ταὐτὸν ἦν τε καὶ ἔστιν μὴ ὄν, ἐνάριθμον τῶν πολλῶν ὄντων εἶδος ἕν.
I say nothing about contrariety (concludes Plato), or about any thing contrary to Ens; nor will I determine whether Non-Ens in this sense be rationally possible or not. What I mean by Non-Ens is a particular case under the general doctrine of the communion or combination of Forms: the combination of Ens with Diversum, composing that which is different from Ens, and which is therefore Non-Ens. Thus Ens itself, being different from all other Forms, is Non-Ens in reference to them all, or an indefinite number of times[119] (i.e. an indefinite number of negative predications may be made concerning it).
[119] Plato, Sophist. pp. 258 E-259 A. ἡμεῖς γὰρ περὶ μὲν ἐναντίου τινὸς αὐτῷ (τῷ ὄντι) χαίρειν πάλαι λέγομεν, εἴτ’ ἔστιν εἴτε μὴ λόγον ἔχον ἢ καὶ παντάπασιν ἄλογον· ὃ δὲ νῦν εἰρήκαμεν εἶναι τὸ μὴ ὄν, &c.