give only the way in which the subject is affected by the object – only certain 'passions' or sensuous modifications of the subject, accompanied by a causal reference to an (otherwise unknown) object.
Now, according to Kant, the human mind is neither purely active nor purer? passive; human knowledge is a compound of receptivity and spontaneity. Kant assumes, on the evidence of mathematics and pure physics, that part of our knowledge possesses universality and necessary validity, and, as universality and necessity cannot be yielded by sense, that the principles of such knowledge must be a priori, drawn in the act of knowledge from the nature of the mind itself. Hence it comes that the crucial question for Kant is, Granted these a priori principles, these notions of the understanding, how can they apply to objects which are given independently of them? If our mode of perception were intellectual or spontaneous throughout, creating its objects whole (both form and matter), there would, of course, be no such difficulty. But our perception being sensuous, dependent for its matter upon foreign objects that exist in their own right, what guarantee have we that ideas which have their source in the mind may be validly applied to independent objects? To the question as thus put there is but one answer – we have no guarantee at all. Kant's way out of the difficulty, therefore, was, in effect, to renounce the attempt to know the real objects and to rest content with the subjective modifications of his own sensibility. That these a posteriori subjective affections should range themselves under the a priori forms of sense and understanding no longer presents any difficulty; on the contrary, it is obvious that the structure of the mind must impress itself on whatever it receives into itself. This fusion of a priori and a posteriori elements yields us the so-called objects of sense – the subjective objects, the phenomena or appearances in us – to which Kant applies the term experience, and to which he limits the scope of our cognition.
It will be seen from what has been said that it was not primarily the subjective origin of the a priori principles that led
