Kant: A Very Short Introduction (Very Short Introductions)

This argument occurs, in more rhetorical form, in the writings of Sartre, whose existentialist doctrine of the moral life owes much to Kant.

and my will is the originator of nothing in the natural world

I can identify experience as mine only if I locate it in time. I must therefore ascribe it to a subject who exists in time and endures through time. My unity requires my continuity. But to endure is to be substantial, and nothing can be substantial unless it also enters into causal relations. I endure only if my past explains my future. Otherwise there is no difference between genuine duration and an infinite sequence of momentary selves. If I can be conscious of my experience at all, I can therefore conclude that I belong to a world to which such categories as substance and cause are correctly applied, since they are correctly applied to me. A condition of self-consciousness is, therefore, the existence of just that objective order which my experience suggests to me.