“But I do not thereby learn whether this consciousness of myself would be at all possible apart from things outside me through which representations are given to me, and whether, therefore, I can exist merely as thinking being (i.e. without existing in human form).”
In B 417-18 Kant points out that rational psychology, in asserting that the self can be conscious apart from all consciousness of outer things, commits itself to the acceptance of problematic idealism. If consciousness of outer objects is not necessary to consciousness of self, there can be no valid method of proving their existence. In the fourth Paralogism of the first edition, the inter-dependence of rational psychology and empirical idealism is also dwelt upon, but is there traced to a confusion of appearances with things in themselves.[1472]
B 410-11.—The correct formulation is here given of what in the first edition[1473] is quite incorrectly stated.[1474] A paralogism is a syllogism which errs in logical form (as contrasted with a syllogism erring in matter, i.e. the premisses of which are false). In the paralogisms of Rational Psychology, the logical fallacy committed is that of ambiguous middle, or as Kant names it, the sophisma figurae dictionis. In the major premiss the middle term is used as referring to real existence, in the minor only as expressive of the unity of consciousness.
Refutation of Mendelssohn’s Proof of the Permanence of the Soul.[1475]—Mendelssohn’s argument is that the soul, as it does not consist of parts,[1476] cannot disappear gradually by disintegration into its constituent elements. If, therefore, it perishes, it must pass out of existence suddenly; at one moment it will exist, at the next moment it will be non-existent. But, Mendelssohn maintains, for three closely connected reasons this would seem to be impossible. In the first place, the immediate juxtaposition of directly opposed states is never to be met with in the material world. Complete opposites, such as day and night, waking and sleeping, never follow upon one another abruptly, but only through a series of intermediate states.[1477] Secondly, among the opposites which material processes thus bridge over, the opposition of being and not-being is never to be found. Only by a miracle can a material existence be annihilated.[1478] If, therefore, empirical evidence is to be allowed as relevant, we must not assert of the invisible soul what is never known to befall the material existences of the visible world. Thirdly—the only part of Mendelssohn’s argument which Kant mentions—the sudden cessation of the soul’s existence would also violate the law of the continuity of time.[1479] Between any two moments there is always an intermediate time in which the one moment passes continuously into the other.
Kant’s reply to this third part of Mendelssohn’s argument is that though the soul must not be conceived as perishing suddenly, it may pass out of existence by a continuous diminution through an infinite number of smaller degrees of intensive reality; and in support of this view he maintains the very doubtful position that clearness and obscurity of representation are not features of the contents apprehended, but only of the intensity of the consciousness directed upon them.[1480]
B 417-22.—Kant here points out that rational psychology, as above expounded, proceeds synthetically, starting from the assertion of the substantiality of the soul and proceeding to the proof that its existence is independent of outer things. But it may proceed in the reverse fashion, analytically developing the implications supposed to be involved in the “I think,” viewed as an existential judgment, i.e. as signifying “I exist thinking.” Kant restates the argument in this analytic form in order, as it would seem, to secure the opportunity of replying to those criticisms of his teaching in the first edition which concern his doctrine of apperception and his employment of the categories, especially of the category of existence, in relation to the self. What is new and important in these pages, and also in the connected passages in B 428-30, has been discussed above.[1481]
B 419-20.—After remarking that simplicity or unity is involved in the very possibility of apperception, Kant proceeds to argue that it can never be explained from a strictly materialist standpoint, since nothing that is real in space is ever simple. Points are merely limits, and are not therefore themselves anything that can form part of space. The passage as a whole would seem to be directed against the Leibnizian teaching of Ulrichs.[1482]
B 426-7.—Kant makes a remark to which nothing in his argument yields any real support, namely, that the dialectical illusion in rational psychology is due to the substitution of an Idea of reason for the quite indeterminate concept of a thinking being in general. As is argued below,[1483] the assumption which he is here making that the concept of the self is an a priori and ultimate Idea of pure Reason, cannot be regarded as a genuine part of his Critical teaching.
B 427-8 touches quite briefly upon questions more fully and adequately treated in the first edition. The scanty treatment here accorded to them would seem to indicate, as Benno Erdmann remarks,[1484] that the problem of the interaction of mind and body which so occupied Kant’s mind from 1747 to 1770 has meantime almost entirely lost interest for him. The problem of immortality remains central, but it is now approached from the ethical side.
In B 421 and B 423-6 Kant draws from his criticism of the Paralogisms the final conclusion that the metaphysical problems as to the nature and destiny of the self are essentially practical problems. When approached from a theoretical standpoint, as curious questions to be settled by logical dialectic, their speculative proof