These two different realms then do not limit each other in their legislation, though they perpetually do so in the world of sense. That they do not constitute _one_ realm, arises from this, that the natural concept represents its objects in intuition, not as things in themselves, but as mere phenomena; the concept of freedom, on the other hand, represents in its Object a thing in itself, but not in intuition. Hence, neither of them can furnish a theoretical knowledge of its Object (or even of the thinking subject) as a thing in itself; this would be the supersensible, the Idea of which we must indeed make the basis of the possibility of all these objects of experience, but which we can never extend or elevate into a cognition. There is, then, an unbounded but also inaccessible field for our whole cognitive faculty--the field of the supersensible--wherein we find no territory, and, therefore, can have in it, for theoretical cognition, no realm either for concepts of Understanding or Reason. This field we must indeed occupy with Ideas on behalf of the theoretical as well as the practical use of Reason, but we can supply to them in reference to the laws [arising] from the concept of freedom no other than practical reality, by which our theoretical cognition is not extended in the slightest degree towards the supersensible. Now even if an immeasurable gulf is fixed between the sensible realm of the concept of nature and the supersensible realm of the concept of freedom, so that no transition is possible from the first to the second (by means of the theoretical use of Reason), just as if they were two different worlds of which the first could have no influence upon the second, yet the second is _meant_ to have an influence upon the first. The concept of freedom is meant to actualise in the world of sense the purpose proposed by its laws, and consequently nature must be so thought that the conformity to law of its form, at least harmonises with the possibility of the purposes to be effected in it according to laws of freedom.--There must, therefore, be a ground of the _unity_ of the supersensible, which lies at the basis of nature, with that which the concept of freedom practically contains; and the concept of this ground, although it does not attain either theoretically or practically to a knowledge of the same, and hence has no peculiar realm, nevertheless makes possible the transition from the mode of thought according to the principles of the one to that according to the principles of the other. III. OF THE CRITIQUE OF JUDGEMENT AS A MEANS OF COMBINING THE TWO PARTS OF PHILOSOPHY INTO A WHOLE.