as things in themselves).  But it does not in the least authorize us to think of it further than as to its formal condition only, that is, the universality of the maxims of the will as laws, and consequently the autonomy of the latter, which alone is consistent with its freedom; whereas, on the contrary, all laws that refer to a definite object give heteronomy, which only belongs to laws of nature, and can only apply to the sensible world.

But Reason would overstep all its bounds if it undertook to explain how pure reason can be practical, which would be exactly the same problem as to explain how freedom is possible.

For we can explain nothing but that which we can reduce to laws, the object of which can be given in some possible experience.  But freedom is a mere Idea [Ideal Conception], the objective reality of which can in no wise be shown according to laws of nature, and consequently not in any possible experience; and for this reason it can never be comprehended or understood, because we cannot support it by any sort of example or analogy.  It holds good only as a necessary hypothesis of reason in a being that believes itself conscious of a will, that is, of a faculty distinct from mere desire (namely, a faculty of determining itself to action as an intelligence), in other words, by laws of reason independently on natural instincts.  Now where determination according to laws of nature ceases, there all explanation ceases also, and nothing remains but defence, i. e. the removal of the objections of those who pretend to have seen deeper into the nature of things, and thereupon boldly declare freedom impossible.  We can only point out to them that the supposed contradiction that they have discovered in it arises only from this, that in order to be able to apply the law of nature to human actions, they must necessarily consider man as an appearance:  then when we demand of them that they should also think of him qua intelligence as a thing in itself, they still persist in considering him in this respect also as an appearance.  In this view it would no doubt be a contradiction to suppose the causality of the same subject (that is, his will) to be withdrawn from all the natural laws of the sensible world.  But this contradiction disappears, if they would only bethink themselves and admit, as is reasonable, that behind the appearances there must also lie at their root (although hidden) the things in themselves, and that we cannot expect the laws of these to be the same as those that govern their appearances.

The subjective impossibility of explaining the freedom of the will is identical with the impossibility of discovering and explaining an interest [Footnote:  Interest is that by which reason becomes practical, i. e., a cause determining the will.  Hence we say of rational beings only that they take an interest in a thing; irrational beings only feel sensual appetites.  Reason takes a direct interest in action then only