beyond the shadow of a doubt, this is to be found in the Transcendental Aesthetics, that is to say, in his doctrine of the ideality of Space and Time.

On such solid foundations is the structure built that no one has been able to raise even an apparent objection. It is Kant's triumph, and belongs to the very small number of metaphysical theories which may be regarded as really proved, and as actual conquests in that field of research. It teaches us that Space and Time are the forms of our own faculty of intuition, to which they consequently belong, and not to the objects thereby perceived; and further, that they can in no way be a condition of things in themselves, but rather attach only to their mode of appearing, such as is alone possible for us who have a consciousness of the external world determined by strictly