[13] B. 49-50 (b) and (c), M. 30 (b) and (c).
[14] Kant here refers to bodies by the term 'phenomena', but their character as phenomena is not relevant to his argument.
[15] It may be noted that Kant's assertion (B. 50, M. 31) that time is the immediate condition of internal phenomena, and thereby also mediately the condition of external phenomena, does not help to reconcile the two positions.
CHAPTER VII
THE METAPHYSICAL DEDUCTION OF THE CATEGORIES
The aim of the Aesthetic is to answer the first question of the Critique propounded in the Introduction, viz. 'How is pure mathematics possible?'[1] The aim of the Analytic is to answer the second question, viz. 'How is pure natural science possible?' It has previously[2] been implied that the two questions are only verbally of the same kind. Since Kant thinks of the judgements of mathematics as self-evident, and therefore as admitting of no reasonable doubt[3], he takes their truth for granted. Hence the question, 'How is pure mathematics possible?' means 'Granted the truth of mathematical judgements, what inference can we draw concerning the nature of the reality to which they relate?'; and the inference is to proceed from the truth of the judgements to the nature of the reality to which they relate. Kant, however, considers that the principles underlying natural science, of which the law of causality is the most prominent, are not self-evident, and consequently need proof.[4] Hence, the question, 'How is pure natural science possible?' means 'What justifies the assertion that the presuppositions of natural science are true?' and the inference is to proceed from the nature of the objects of natural science to the truth of the a priori judgements which relate to them.
Again, as Kant rightly sees, the vindication of the presuppositions of natural science, to be complete, requires the discovery upon a definite principle of all these presuppositions. The clue to this discovery he finds in the view that, just as the perceptions of space and time originate in the sensibility, so the a priori conceptions and laws which underlie natural science originate in the understanding; for, on this view, the discovery of all the conceptions and laws which originate in the understanding will be at the same time the discovery of all the presuppositions of natural science.
Kant therefore in the Analytic has a twofold problem to solve. He has firstly to discover the conceptions and laws which belong to the understanding as such, and secondly to vindicate their application to individual things. Moreover, although it is obvious that the conceptions and the laws of the understanding must be closely related,[5] he reserves them for separate treatment.