The celebrated Locke, for want of due reflection on these points, and because he met with pure conceptions of the understanding in experience, sought also to deduce them from experience, and yet proceeded so inconsequently as to attempt, with their aid, to arrive it cognitions which lie far beyond the limits of all experience.David Hume perceived that, to render this possible, it was necessary that the conceptions should have an a priori origin.But as he could not explain how it was possible that conceptions which are not connected with each other in the understanding must nevertheless be thought as necessarily connected in the object- and it never occurred to him that the understanding itself might, perhaps, by means of these conceptions, be the author of the experience in which its objects were presented to it- he was forced to drive these conceptions from experience, that is, from a subjective necessity arising from repeated association of experiences erroneously considered to be objective-in one word, from habit.But he proceeded with perfect consequence and declared it to be impossible, with such conceptions and the principles arising from them, to overstep the limits of experience.The empirical derivation, however, which both of these philosophers attributed to these conceptions, cannot possibly be reconciled with the fact that we do possess scientific a priori cognitions, namely, those of pure mathematics and general physics.
The former of these two celebrated men opened a wide door to extravagance- (for if reason has once undoubted right on its side, it will not allow itself to be confined to set limits, by vague recommendations of moderation); the latter gave himself up entirely to scepticism- a natural consequence, after having discovered, as he thought, that the faculty of cognition was not trustworthy.We now intend to make a trial whether it be not possible safely to conduct reason between these two rocks, to assign her determinate limits, and yet leave open for her the entire sphere of her legitimate activity.
I shall merely premise an explanation of what the categories are.
They are conceptions of an object in general, by means of which its intuition is contemplated as determined in relation to one of the logical functions of judgement.The following will make this plain.
The function of the categorical judgement is that of the relation of subject to predicate; for example, in the proposition: "All bodies are divisible." But in regard to the merely logical use of the understanding, it still remains undetermined to which Of these two conceptions belongs the function Of subject and to which that of predicate.For we could also say: "Some divisible is a body." But the category of substance, when the conception of a body is brought under it, determines that; and its empirical intuition in experience must be contemplated always as subject and never as mere predicate.
And so with all the other categories.
SECTION II Transcendental Deduction of the pure Conceptions of the Understanding.SS 11Of the Possibility of a Conjunction of the manifold representations given by Sense.
The manifold content in our representations can be given in an intuition which is merely sensuous- in other words, is nothing but susceptibility; and the form of this intuition can exist a priori in our faculty of representation, without being anything else but the mode in which the subject is affected.But the conjunction (conjunctio) of a manifold in intuition never can be given us by the senses; it cannot therefore be contained in the pure form of sensuous intuition, for it is a spontaneous act of the faculty of representation.And as we must, to distinguish it from sensibility, entitle this faculty understanding; so all conjunction whether conscious or unconscious, be it of the manifold in intuition, sensuous or non-sensuous, or of several conceptions- is an act of the understanding.To this act we shall give the general appellation of synthesis, thereby to indicate, at the same time, that we cannot represent anything as conjoined in the object without having previously conjoined it ourselves.Of all mental notions, that of conjunction is the only one which cannot be given through objects, but can be originated only by the subject itself, because it is an act of its purely spontaneous activity.The reader will easily enough perceive that the possibility of conjunction must be grounded in the very nature of this act, and that it must be equally valid for all conjunction, and that analysis, which appears to be its contrary, must, nevertheless, always presuppose it; for where the understanding has not previously conjoined, it cannot dissect or analyse, because only as conjoined by it, must that which is to be analysed have been given to our faculty of representation.
But the conception of conjunction includes, besides the conception of the manifold and of the synthesis of it, that of the unity of it also.Conjunction is the representation of the synthetical unity of the manifold.* This idea of unity, therefore, cannot arise out of that of conjunction; much rather does that idea, by combining itself with the representation of the manifold, render the conception of conjunction possible.This unity, which a priori precedes all conceptions of conjunction, is not the category of unity (SS 6); for all the categories are based upon logical functions of judgement, and in these functions we already have conjunction, and consequently unity of given conceptions.It is therefore evident that the category of unity presupposes conjunction.We must therefore look still higher for this unity (as qualitative, SS 8), in that, namely, which contains the ground of the unity of diverse conceptions in judgements, the ground, consequently, of the possibility of the existence of the understanding, even in regard to its logical use.