2. Sigwart, in seeking the consciousness of insight in a feeling of necessity so to think, asserts that the consciousness of one’s being compelled is, at the same time, a consciousness of a necessity for all thinking beings whenever the same grounds are present. If he means, however, that the one conviction is doubtless connected with the other, this is an error. Why, when a person feels bound to pass a judgment upon certain data, should the same compulsion hold good in respect of every other thinking being to whom the same data are also given? It is obvious that only an appeal to the law of causality which, under like conditions demands like results, could be the ground of the logical connexion. Its application, however, to the present case would be entirely erroneous, since this would involve the ignoring of the special psychical dispositions, which, although they do not directly enter into consciousness at all, must yet be regarded, along with the conscious data, as pre-determining conditions, and these are very different in the case of different persons. Hegel and his school, misled by paralogisms, have denied the principle of contradiction; Trendelenburg, who opposed Hegel, has at least restricted its validity (cf. his _Abhandlungen über Herbarts Metaphysik_). The universal impossibility of inwardly denying the principle which Aristotle asserted cannot therefore, to-day, be any longer defended; Aristotle himself, however, for whom the principle was self-evident, assuredly found its denial impossible. Whatever is evident to any one is of course certain not only for him, but also for every one else who, in the same way, sees its evidence. The judgment, moreover, which is seen to be evident by any one has also universal validity, i.e. the contradictory of what is seen to be evident by one person, cannot be seen to be evident by another person, and every one who believes in its contradictory is in error. Further, since what is here said belongs to the essence of truth, whoever has evidence of the truth of anything may perceive that he is justified in regarding it as true for all. But he would be guilty of a flagrant confusion of ideas who should regard such a consciousness that a truth is true for all, as equivalent to a consciousness of a universal necessity of thinking.