Kant to pronounce our knowledge merely phenomenal. It is rather to our sensuous or receptive attitude in cognition that the phenomenalistic taint is due. It is due to this fundamental characteristic of human intelligence, rather than to any defect inherent in themselves, that the categories are strictly limited to a phenomenal or subjective world; they are empty, as Kant says, without the filling of sense. But though Kant's phenomenalism has thus its roots in his view of the a posteriori even more than in his account of the a priori, his theory of the a priori is unquestionably what gives his system its distinctive character. But for mathematics and physics and Hume's sceptical analysis of necessary truth, Kant might have remained content with a theory like Locke's. Locke gives a substantially similar account of a posteriori knowledge, but the sceptical implications of 'the theory of ideas' have not yet developed themselves. The connection is closer between the ideas and their real causes or prototypes – which Locke, indeed, believes them faithfully to represent, so far at least, as the primary qualities are concerned. The elaboration of the a priori element by Kant, and the prominence given to it in the constitution of the so-called object of sense, inevitably widens the gulf between ideas and things, between the phenomenon and the thing-in-itself. The phenomenal object, drawing so many of its determinations from the subject, becomes detached from the object whose appearance it is supposed to be, but which, be it observed, it no longer represents. It becomes a satellite of the mind, a mental object. And eventually, under cover of the ambiguous terms 'object' and 'experience,' it assumes a quasi-independence of the mind also, and is then ready to do duty for the real things of science and common life.
We need not wonder, then, that, in the course of the exposition, the thing-in-itself, the transcendent cause of our experience, falls into the background. It falls into the background not because it is any the less supposed to be there, but because Kant is not interested in the particular matter of sense of which it is the source and explanation. He is altogether absorbed in vindicating, in view of Hume, the universal and
