The general view taken by Zeller of the Platonic Parmenides, is repeated by him in his Phil. der Griech. vol. ii. pp. 394-415-429, ed. 2nd. In the first place, I do not think that he sets forth exactly (see p. 415) the reasoning as we read it in Plato; but even if that were exactly set forth, still what we read in Plato is nothing but an assemblage of difficulties and contradictions. These are indeed suggestive, and such as a profound critic may meditate with care, until he finds himself put upon a train of thought conducting him to conclusions sound and tenable in his judgment. But the explanations, sufficient or not, belong after all not to Plato but to the critic himself. Other critics may attach, and have attached, totally different explanations to the same difficulties. I see no adequate evidence to bring home any one of them to Plato; or to prove (what is the main point to be determined) that any one of them was present to his mind when he composed the dialogue.
Schwegler also gives an account of what he affirms to be the purpose and meaning of the Parmenides — “The positive meaning of the antinomies contained in it can only be obtained by inferences which Plato does not himself expressly enunciate, but leaves to the reader to draw” (Geschichte der Philosophie im Umriss, sect. 14, 4 c. pp. 52-53, ed. 5).
A learned man like Schwegler, who both knows the views of other philosophers, and has himself reflected on philosophy, may perhaps find affirmative meaning in the Parmenides; just as Sokrates, in the Platonic Protagoras, finds his own ethical doctrine in the song of the poet Simonides. But I venture to say that no contemporary reader of Plato could have found such a meaning in the Parmenides; and that if Plato intended to communicate such a meaning, the whole structure of the dialogue would be only an elaborate puzzle calculated to prevent nearly all readers from reaching it.
By assigning the leadership of the dialogue to Parmenides (Schwegler says) Plato intends to signify that the Platonic doctrine of Ideas is coincident with the doctrine of Parmenides, and is only a farther development thereof. How can this be signified, when the discourse assigned to Parmenides consists of a string of objections against the doctrine of Ideas, concluding with an intimation that there are other objections, yet stronger, remaining behind?
The fundamental thought of the Parmenides (says Schwegler) is, that the One is not conceivable in complete abstraction from the Many, nor the Many in complete abstraction from the One, — that each reciprocally supposes and serves as condition to the other. Not so: for if we follow the argumentation of Parmenides (p. 131 E), we shall see that what he principally insists upon, is the entire impossibility of any connection or participation between the One and the Many — there is an impassable gulf between them.
Is the discussion of τὸ ἓν (in the closing Antinomies) intended as an example of dialectic investigation — or is it per se the special object of the dialogue? This last is clearly the truth (says Schwegler). “otherwise the dialogue would end without result, and its two portions would be without any internal connection”. Not so; for if we read the dialogue, we find Parmenides clearly proclaiming and singling out τὸ ἓν as only one among a great many different notions, each of which must be made the subject of a bilateral hypothesis, to be followed out into its consequences on both sides (p. 136 A). Moreover, I think that the “internal connection” between the first and the last half of the dialogue, consists in the application of this dialectic method, and in nothing else. If the dialogue ends without result, this is true of many other Platonic dialogues. The student is brought face to face with logical difficulties, and has to find out the solution for himself; or perhaps to find out that no solution can be obtained.
[55] Plato, Parmenid. p. 135 C.
This negative purpose is expressly announced by Plato himself. All dogmatical purpose, extending farther, is purely hypothetical, and even inconsistent with what is declared.
Such, in my judgment, is the drift of the contradictory demonstrations here put into the mouth of Parmenides respecting Unum and Cætera. Thus far at least, we are perfectly safe: for we are conforming strictly to the language of Plato himself in the dialogue: we have no proof that he meant anything more. Those who presume that he must have had some ulterior dogmatical purpose, place themselves upon hypothetical ground: but when they go farther and attempt to set forth what this purpose was, they show their ingenuity only by bringing out what they themselves have dropped in. The number of discordant hypotheses attests[56] the difficulty of the problem. I agree with those early Platonic commentators (mentioned and opposed by Proklus) who could see no other purpose in these demonstrations than that of dialectical exercise. In this view Schleiermacher, Ast, Strümpell, and others mainly concur: the two former however annexing to it a farther hypothesis — which I think improbable — that the dialogue has come to us incomplete; having once contained at the end (or having been originally destined to contain, though the intention may never have been realised) an appendix elucidating the perplexities of the demonstrations.[57] This would have been inconsistent with the purpose declared by Parmenides: who, far from desiring to facilitate the onward march of Sokrates by clearing up difficulties, admonishes him that he is advancing too rapidly, and seeks to keep him back by giving him a heap of manifest contradictions to disentangle. Plato conceives the training for philosophy or for the highest exercise of intellectual force, to be not less laborious than that which was required for the bodily perfections of an Olympic athlete. The student must not be helped out of difficulties at once: he must work his own way slowly out of them.
[56] Proklus ad Platon. Parmen. I. pp. 482-485, ed. Stallb.; compare pp. 497-498-788-791, where Proklus is himself copious upon the subject of exercise in dialectic method.