A Commentary to Kant's 'Critique of Pure Reason'

by Norman Kemp Smith

The key to the whole problem of the four questions is not to be found in the Critique. This section is transcribed from §§ 4-5 of the Prolegomena, and is consequently influenced by the general arrangement of the latter work. This fourfold division was indeed devised for the purposes of the argument of the Prolegomena, which is developed on the analytic method, and for that reason it cannot be reconciled with the very different structure of the Critique. Yet even the Prolegomena suffers from confusion, due[303] to Kant’s failure to distinguish between universal and relative natural science on the one hand, and between immanent and transcendent metaphysics on the other. The four questions do not coincide with those of the Critique. Instead of the third—how is metaphysics as natural disposition possible?—we find: how is metaphysics in general possible? In §§ 4, 5, Kant’s argument is clear and straightforward. Pure mathematical science and mathematical physics are actually existing sciences. The synthetic a priori judgments which they contain must be recognised as valid. Metaphysics makes similar claims. But, as is sufficiently proved by the absence of agreement among philosophers, its professions are without ground. It transgresses the limits of possible experience, and contains only pretended knowledge. This false transcendent metaphysics is refuted in the Dialectic. Kant was, however, equally convinced that an immanent metaphysics is possible, and that its grounds and justification had been successfully given in the Analytic. His problem as formulated in the Prolegomena is accordingly threefold: (1) how are the existing rational sciences, mathematical and physical, possible? (2) in the light of the insight acquired by this investigation, what is the origin and explanation of the existing pretended sciences of transcendent metaphysics? and (3) in what manner can we establish a positive metaphysics that will harmonise with reason’s true vocation? So far all is clear and definite. But the unresolved difficulty, as to the relation in which natural science and immanent metaphysics stand to one another, brings confusion in its train. As already noted,[304] in § 15 natural science is displaced by immanent metaphysics (though not under that name); and as a result the fourth question reduces to the second, and the above threefold problem has to be completely restated. The Prolegomena has, however, already been divided into four parts; and in the last division Kant still continues to treat the fourth question as distinct from that which has been dealt with in the second division, though, as his answer shows, they are essentially the same. The answer given is that metaphysics as a science is possible only in and through the Critique, and that though the whole Critique is required for this purpose, the content of the new science is embodied in the Analytic.

In the second edition of the Critique the confusion between natural science and immanent metaphysics still persists, and a new source of ambiguity is added through the reformulation of the third question. It is now limited to the problem of the subjective origin of metaphysics as a natural disposition. The fourth question has therefore to be widened, so as to include transcendent as well as immanent, the old as well as the new, metaphysics. But save for this one alteration the entire section is inspired by considerations foreign to the Critique; this section, like B 17, must be recast before it will harmonise with the subsequent argument.

Every kind of knowledge is called pure, etc.[305]—These sentences are omitted in the second edition. They have been rendered unnecessary by the further and more adequate definition of “pure” given in B 3 ff.

Reason is the faculty which supplies the principles of knowledge a priori.[306]—This statement should, as Vaihinger points out, be interpreted in the light of A 299 = B 355.

“Reason, like understanding, can be employed in a merely formal, i.e. logical manner, wherein it abstracts from all content of knowledge. But it is also capable of a real use,[307] since it contains within itself the source of certain concepts and principles, which it does not borrow either from the senses or from the understanding.”

Reason is taken in the first of the above meanings. Reason in its real use, when extended so as to include pure sensibility and understanding,[308] is the pure reason referred to in the next sentence of the Critique. A priori is here used to signify the relatively a priori; in the next sentence it denotes the absolutely a priori.

An Organon of pure reason.[309]—What follows, from this point to the middle of the next section, is a good example of Kant’s patchwork method of piecing together old manuscript in the composition of the Critique. There seems to be no way of explaining its bewildering contradictions save by accepting Vaihinger’s[310] conclusion that it consists of three separate accounts, written at different times, and representing different phases in the development of Kant’s views.

I. The first account, beginning with the above words and ending with “already a considerable gain” (schon sehr viel gewonnen ist), is evidently the oldest. It reveals the influence of the Dissertation. It distinguishes:

1. Critique of pure reason ( = Propaedeutic).
2. Organon of pure reason.
3. System of pure reason.

1. Critique is a critical examination (Beurtheilung) of pure reason, its sources and limits. The implication (obscured by the direct relating of Critique to System) is that it prepares the way for the Organon.