So also, in regard to the intercommunion of Forms, skill and art are required to decide which of them will come together, and which will not. In every special art and profession the case is similar: the ignorant man will fail in deciding this question — the man of special skill alone will succeed. — So in regard to the intercommunion of Forms or Genera universally with each other, the comprehensive science of the true philosopher is required to decide.[58] To note and study these Forms, is the purpose of the philosopher in his dialectics or ratiocinative debate. He can trace the one Form or Idea, stretching through a great many separate particulars; he can distinguish it from all different Forms: he knows which Forms are not merely distinct from each other, but incapable of alliance and reciprocally repulsive — which of them are capable of complete conjunction, the one circumscribing and comprehending the other — and which of them admit conjunction partial and occasional with each other.[59] The philosopher thus keeps close to the Form of eternal and unchangeable Ens or Reality — a region of such bright light that the eyes of the vulgar cannot clearly see him: while the Sophist on the other hand is also difficult to be seen, but for an opposite reason — from the darkness of that region of Non-Ens or Non-Reality wherein he carries on his routine-work.[60]
[58] Plato, Sophist. p. 253 B. ἆρ’ οὐ μετ’ ἐπιστήμης τινὸς ἀναγκαῖον διὰ τῶν λόγων πορεύεσθαι τὸν ὀρθῶς μέλλοντα δείξειν ποῖα ποίοις συμφωνεῖ τῶν γενῶν καὶ ποῖα ἄλληλα οὐ δέχεται;
[59] Plato, Sophist. p. 253 D-E.
[60] Plato, Sophist. p. 254 A. Ὁ δέ γε φιλόσοφος, τῇ τοῦ ὄντος ἀεὶ διὰ λογισμῶν προσκείμενος ἰδέᾳ, διὰ τὸ λαμπρὸν αὖ τῆς χώρας οὐδαμῶς εὐπέτης ὀφθῆναι· τὰ γὰρ τῆς τῶν πολλῶν ψυχῆς ὄμματα καρτερεῖν πρὸς τὸ θεῖον ἀφορῶντα ἀδύνατα.
He comes to enquire what Non-Ens is. He takes for examination five principal Forms — Motion — Rest — Ens — Same — Different.
We have still to determine, however (continues Plato), what this Non-Ens or Non-Reality is. For this purpose we will take a survey, not of all Forms or Genera, but of some few the most important. We will begin with the two before noticed — Motion and Rest ( = Change and Permanence), which are confessedly irreconcileable and reciprocally exclusive. Ens however enters into partnership with both: for both of them are, or exist.[61] This makes up three Forms or Genera — Motion, Rest, Ens: each of the three being the same with itself, and different from the other two. Here we have pronounced two new words — Same — Different.[62] Do these words designate two other Forms, over and above the three before-named, yet necessarily always intermingling in partnership with those three, so as to make five Forms in all? Or are these two — Same and Different — essential appendages of the three before-named? This last question must be answered in the negative. Same and Different are not essential appendages, or attached as parts, to Motion, Rest, Ens. Same and Different may be predicated both of Motion and of Rest: and whatever can be predicated alike of two contraries, cannot be an essential portion or appendage of either. Neither Motion nor Rest therefore are essentially either Same or Different: though both of them partake of Same or Different — i.e., come into accidental co-partnership with one as well as the other.[63] Neither can we say that Ens is identical with either Idem or Diversum. Not with Idem — for we speak of both Motion and Rest as Entia or Existences: but we cannot speak of them as the same. Not with Diversum — for different is a name relative to something else from which it is different, but Ens is not thus relative. Motion and Rest are or exist, each in itself: but each is different, relatively to the other, and to other things generally. Accordingly we have here five Forms or Genera — Ens, Motion, Rest, Idem, Diversum: each distinct from and independent of all the rest.[64]
[61] Plato, Sophist. p. 254 D. τὸ δέ γε ὂν μικτὸν ἀμφοῖν· ἐστὸν γὰρ ἄμφω που.
[62] Plato, Sophist. p. 254 E. τί ποτ’ αὖ νῦν οὕτως εἰρήκαμεν τό τε ταὐτὸν καὶ θάτερον; πότερα δύο γένη τινὲ αὐτώ, τῶν μὲν τριῶν ἄλλω, &c.
[63] Plato, Sophist. p. 255 B. μετέχετον μὴν ἄμφω ταὐτοῦ καὶ θατέρου … Μὴ τοίνυν λέγωμεν κίνησίν γ’ εἶναι ταὐτὸν ἢ θάτερον, μηδ’ αὖ στάσιν.
[64] Plato, Sophist. p. 255 D.