Note 113 — Chapter XXIX · SOPHISTES — POLITIKUS.
Reading edition
Plato, Sophist. p. 255 B.
Μετέχετον μὴν ἄμφω (κίνησις καὶ στάσις) ταὐτοῦ καὶ θατέρου.…
Μὴ τοίνυν λέγωμεν κίνησιν γ’ εἶναι ταὐτὸν ἢ θάτερον, μηδ’ αὖ στάσιν. He had before said — Ἀλλ’ οὔ τι μὴν κίνησίς γε καὶ στάσις οὐθ’ ἕτερον οὔτε ταὐτόν ἐστιν (p. 255 A).
Plato here says, It is true that κίνησις μετέχει ταὐτοῦ, but it is not true that κίνησίς ἐστι ταὐτόν. Again, p. 259 A. τὸ μὲν ἕτερον μετασχὸν τοῦ ὄντος ἔστι μὲν διὰ ταύτην τὴν μέθεξιν, οὐ μὴν ἐκεῖνό γε οὖ μετέσχεν ἀλλ’ ἕτερον. He understands, therefore, that ἐστι, when used as copula, implies identity between the predicate and the subject.
This is the same point of view from which Antisthenes looked, when he denied the propriety of saying Ἄνθρωπός ἐστιν ἀγαθός — Ἄνθρωπός ἐστι κακός: and when he admitted only identical propositions, such as Ἄνθρωπός ἐστιν ἄνθρωπος — Ἄγαθός ἐστιν ἀγαθός. He assumed that ἐστι, when intervening between the subject and the predicate, implies identity between them; and the same assumption is made by Plato in the passage now before us. Whether Antisthenes would have allowed the proposition — Ἄνθρωπος μετέχει κακίας, or other propositions in which ἐστι does not appear as copula, we do not know enough of his opinions to say.
Compare Aristotel. Physic. i. 2, 185, b. 27, with the Scholia of Simplikius, p. 330, a. 331, b. 18-28, ed. Brandis.