The second point against which Plato argues is the dialectic of the Eleatics, and their assertion, which in its nature resembles that of the Sophists, that only Being is, and non-being is not. To the Sophists this means, as Plato puts it: Since the negative is not, but only Being is, there is nothing false; everything existent, everything which is for us, is thus necessarily true, and what is not, we do not know or feel. Plato reproaches the Sophists for thus doing away with the difference between true and false.[39] Having arrived at this stage in the knowledge of the dialectic (and the whole matter is merely a difference of stages) the Sophists could allow what they promise—that everything that the individual, according to his belief, makes his end and interest, is affirmative and right. Hence it cannot be said that such and such an act is wrong, wicked, a crime; for this would be to say that the maxim of the action is wrong. No more can it be said that such and such opinion is deceptive, for in the opinion of the Sophists the proposition implies that what I feel or represent to myself, in as far as it is mine, is an affirmative content, and thus true and right. The proposition in itself seems quite abstract and innocent, but we first notice what is involved in such abstractions when we see them in concrete form. According to this innocent proposition there would be no wickedness and no crime. The Platonic dialectic is essentially different from this kind of dialectic.
What is further present to the mind of Plato is that the Idea, the absolute universal, good, true, and beautiful, is to be taken for itself. The myth, which I have already quoted (p. 27 _et seq._), indeed goes to prove that we must not consider a good action, a noble man—not the subject of which these determinations are predicated. For that which appears in such conceptions or perceptions as predicate, must be taken for itself, and this is the absolute truth. This tallies with the nature of the dialectic which has been described. An action, taken in accordance with the empirical conception, may be called right; in another aspect, quite opposite determinations may be shown to be in it. But the good and true must be taken on their own account without such individualities, without this empirical and concrete character; and the good and true thus taken alone, constitute that which is. The soul which, according to the divine drama, is found in matter, rejoices in a beautiful and just object; but the only actual truth is in absolute virtue, justice, and beauty. It is thus the universal for itself which is further determined in the Platonic dialectic; of this several forms appear, but these forms are themselves still very general and abstract. Plato’s highest form is the identity of Being and non-being. The true is that which is, but this Being is not without negation. Plato’s object is thus to show that non-being is an essential determination in Being, and that the simple, self-identical, partakes of other-being. This unity of Being and non-being is also found in the Sophists; but this alone is not the end of the matter. For in further investigation Plato comes to the conclusion that non-being, further determined, is the essence of the ‘other’: “Ideas mingle, and Being and the other (θάτερον) go through everything and through one another; the other, because it participates (μετασχόν) in Being, certainly _is_ through this indwelling Being, but it is not identical with that of which it partakes, being something different, and being other than Being, it is clearly non-being. But since Being likewise partakes of other-being, it also is different from other Ideas, and is not any one of them; so that there are thousands of ways in which it is not, and as regards all else, whether looked at individually or collectively, it in many respects is, and in many respects is not.”[40] Plato thus maintains that the other, as the negative, non-identical, is likewise in one and the same respect the self-identical; there are not different sides which are in mutual opposition.