Non-Ens being thus shown to be one among the many other Forms, disseminated among all the others, and entering into communion with Ens among the rest — we have next to enquire whether it enters into communion with the Form of Opinion and Discourse. It is the communion of the two which constitutes false opinion and false proposition: if therefore such communion be possible, false opinion and false proposition are possible, which is the point that Plato is trying to prove.[120]
[120] Plato, Sophist. p. 260 B.
Communion of Non-Ens with proposition — possible and explicable.
Now it has been already stated (continues Plato) that some Forms or Genera admit of communion with each other, others do not. In like manner some words admit of communion with each other — not others. Those alone admit of communion, which, when put together, make up a proposition significant or giving information respecting Essence or Existence. The smallest proposition must have a noun and a verb put together: the noun indicating the agent, the verb indicating the act. Every proposition must be a proposition concerning something, or must have a logical subject: every proposition must also be of a certain quality. Let us take (he proceeds) two simple propositions: Theætêtus is sitting down — Theætêtus is flying.[121] Of both these two, the subject is the same: but the first is true, the second is false. The first gives things existing as they are, respecting the subject: the second gives respecting the subject, things different from those existing, or in other words things non-existent, as if they did exist.[122] A false proposition is that which gives things different as if they were the same, and things non-existent as if they were existent, respecting the subject.[123]
[121] Plato, Sophist. p. 263 A. Θεαίτητος κάθηται … Θεαίτητος πέτεται.
[122] Plato, Sophist. p. 263 B. λέγει δὲ αὐτῶν (τῶν λόγων of the two propositions) ὁ μὲν ἀληθὴς τὰ ὄντα, ὡς ἐστι περὶ σοῦ … Ὁ δὲ δὴ ψευδὴς ἕτερα τῶν ὄντων … Τὰ μὴ ὄντ’ ἄρα ὡς ὄντα λέγει … Ὄντων δέ γε ὄντα ἕτερα περὶ σοῦ. Πολλὰ μὲν γὰρ ἔφαμεν ὄντα περὶ ἕκαστον εἶναί που, πολλὰ δὲ οὐκ ὄντα.
[123] Plato, Sophist. p. 263 D. Περὶ δὴ σοῦ λεγόμενα μέντοι θάτερα ὡς τὰ αὐτά, καὶ μὴ ὄντα ὡς ὄντα, παντάπασιν, ὡς ἔοικεν, ἡ τοιαύτη σύνθεσις ἔκ τε ῥημάτων γιγνομένη καὶ ὀνομάτων ὄντως τε καὶ ἀληθῶς γίγνεσθαι λόγος ψευδής.
It is plain that this explanation takes no account of negative propositions: it applies only to affirmative propositions.
Imperfect analysis of a proposition — Plato does not recognise the predicate.
The foregoing is Plato’s explanation of Non-Ens. Before we remark upon it, let us examine his mode of analysing a proposition. He conceives the proposition as consisting of a noun and a verb. The noun marks the logical subject, but he has no technical word equivalent to subject: his phrase is, that a proposition must be of something or concerning something. Then again, he not only has no word to designate the predicate, but he does not even seem to conceive the predicate as distinct and separable: it stands along with the copula embodied in the verb. The two essentials of a proposition, as he states them, are — That it should have a certain subject — That it should be of a certain quality, true or false.[124] This conception is just, as far as it goes: but it does not state all which ought to be known about proposition, and it marks an undeveloped logical analysis. It indicates moreover that Plato, not yet conceiving the predicate as a distinct constituent, had not yet conceived the copula as such: and therefore that the substantive verb ἔστιν had not yet been understood by him in its function of pure and simple copula. The idea that the substantive verb when used in a proposition must mark existence or essence, is sufficiently apparent in several of his reasonings.