[1] At the beginning of the Politikus, Plato makes Sokrates refer both to the Theætêtus and to the Sophistês (p. 258 A). In more than one passage of the Politikus (pp. 266 D, 284 B, 286 B), he even refers to the Sophistês directly and by name, noticing certain points touched in it — a thing very unusual with him. In the Sophistês also (p. 233 B), express reference is made to a passage in the Theætêtus.
See also the allusion in Sophistês (to the appearance of the younger Sokrates as respondent), p. 218 B.
Socher (in his work, Ueber Platon’s Schriften, pp. 258-294) maintains that neither the Sophistês, nor the Politikus, nor the Parmenidês, are genuine works of Plato. He conceives the two dialogues to be contemporary with the Theætêtus (which he holds to have been written by Plato), but to have been composed by some acute philosopher of the Megaric school, conversant with the teachings of Sokrates and with the views of Plato, after the visit of the latter to Megara in the period succeeding the death of Sokrates (p. 268).
Even if we grant the exclusion of Plato’s authorship, the hypothesis of an author belonging to the Megaric school is highly improbable: the rather, since many critics suppose (I think erroneously) that the Megarici are among those attacked in the dialogue. The suspicion that Plato is not the author of Sophistês and Politikus has undoubtedly more appearance of reason than the same suspicion as applied to other dialogues — though I think the reasons altogether insufficient. Socher observes, justly: 1. That the two dialogues are peculiar, distinguished from other Platonic dialogues by the profusion of logical classification, in practice as well as in theory. 2. That both, and especially the Sophistês, advance propositions and conclusions discrepant from what we read in other Platonic dialogues. — But these two reasons are not sufficient to make me disallow them. I do not agree with those who require so much uniformity, either of matter or of manner, in the numerous distinct dialogues of Plato. I recognise a much wider area of admissible divergence.
The plain announcement contained in the Theætêtus, Sophistês, and Politikus themselves, that the two last are intended as sequel to the first, is in my mind a proof of sameness of authorship, not counterbalanced by Socher’s objections. Why should a Megaric author embody in his two dialogues a false pretence and assurance, that they are sequel of the Platonic Theætêtus? Why should so acute a writer (as Socher admits him to be) go out of his way to suppress his own personality, and merge his fame in that of Plato?
I make the same remark on the views of Suckow (Form der Platonischen Schriften, p. 87, seq., Breslau, 1855), who admits the Sophistes to be a genuine work of Plato, but declares the Politikus to be spurious; composed by some fraudulent author, who wished to give to his dialogue the false appearance of being a continuation of the Sophistes: he admits (p. 93) that it must be a deliberate deceit, if the Politikus be really the work of a different author from the Sophistês; for identity of authorship is distinctly affirmed in it.
Suckow gives two reasons for believing that the Politikus is not by Plato:— 1. That the doctrines respecting government are different from those of the Republic, and the cosmology of the long mythe which it includes different from the cosmology of the Timæus. These are reasons similar to those advanced by Socher, and (in my judgment) insufficient reasons. 2. That Aristotle, in a passage of the Politica (iv. 2, p. 1289, b. 5), alludes to an opinion, which is found in the Politikus in the following terms: ἤδη μὲν οὖν τις ἀπεφήνατο καὶ τῶν πρότερον οὕτως, &c. Suckow maintains that Aristotle could never have alluded to Plato in these terms, and that he must have believed the Politikus to be composed by some one else. But I think this inference is not justified by the premisses. It is noway impossible that Aristotle might allude to Plato sometimes in this vague and general way: and I think that he has done so in other passages of the same treatise (vii. 2, 1324, a. 29 — vii. 7, p. 1327, b. 37).
Ueberweg (Aechtheit der Platon. Schrift. p. 162, seq.) combats with much force the views of Suckow. It would be rash to build so much negative inference upon a loose phrase of Aristotle. That he should have spoken of Plato in this vague manner is much more probable, or much less improbable, than the counter-supposition, that the author of a striking and comprehensive dialogue, such as the Politikus, should have committed a fraud for the purpose of fastening his composition on Plato, and thus abnegating all fame for himself.
The explicit affirmation of the Politikus itself ought to be believed, in my judgment, unless it can be refuted by greater negative probabilities than any which Socher and Suckow produce. I do not here repeat, what I have endeavoured to justify in an earlier [chapter] of this work, the confidence which I feel in the canon of Thrasyllus; a confidence which it requires stronger arguments than those of these two critics to overthrow.
[2] Plato, Sophist. p. 216 B-C.