In this inquiry criticism may and must begin with pure practical laws and their reality. But instead of intuition it takes as their foundation the conception of their existence in the intelligible world, namely, the concept of freedom. For this concept has no other meaning, and these laws are only possible in relation to freedom of the will; but freedom being supposed, they are necessary; or conversely freedom is necessary because those laws are necessary, being practical postulates. It cannot be further explained how this consciousness of the moral law, or, what is the same thing, of freedom, is possible; but that it is admissible is well established in the theoretical critique. The exposition of the supreme principle of practical reason is now finished; that is to say, it has been shown first, what it contains, that it subsists for itself quite a priori and independent of empirical principles; and next in what it is distinguished from all other practical principles. With the deduction, that is, the justification of its objective and universal validity, and the discernment of the possibility of such a synthetical proposition a priori, we cannot expect to succeed so well as in the case of the principles of pure theoretical reason. For these referred to objects of possible experience, namely, to phenomena, and we could prove that these phenomena could be known as objects of experience only by being brought under the categories in accordance with these laws; and consequently that all possible experience must conform to these laws. But I could not proceed in this way with the deduction of the moral law. For this does not concern the knowledge of the properties of objects, which may be given to the reason from some other source; but a knowledge which can itself be the ground of the existence of the objects, and by which reason in a rational being has causality, i.e., pure reason, which can be regarded as a faculty immediately determining the will.