Prolegomena to Any Future Metaphysics Third Part, Sections 50–56 Summary & Analysis

The mistake in the case of (1) comes from treating space and time as things in themselves rather than as intuitions of our faculty of sensibility. Space and time are features of our experience, and do not exist independently of experience. It makes no sense to ask whether or not the world has a limit in space and time, since that limit would exist outside the realm of our experience.

In (2), when we talk about the parts into which a composite thing can be divided, we are assuming that these already exist, waiting inside the composite thing. But these parts are only appearances, and so cannot have any existence until they are experienced.

In (3), causal necessity and freedom are made to seem contradictory when in fact they are compatible. The laws of nature can only operate within the confines of space and time, and so are applicable only to appearances. Freedom, on the other hand, is the ability to outside the confines of causality, and so to exist outside the confines of experience. Freedom, then, is applicable only to things in themselves.

Our faculty of reason does not deal with experience, and so we are free in our capacity as rational beings. This freedom must express itself only in general maxims that do not depend on causal influence or particular times and places. In obeying these general maxims, we still follow regular laws in the world of appearances. Thus, we can be free and also be subject to the laws of nature.

The seeming contradiction in (4) is similarly resolved if we see that one half of the proposition talks about things in themselves and the other half of the proposition talks about appearances. In the world of appearances, every causal connection may be contingent, which is to say it could have happened otherwise. Nonetheless, these appearances might have a necessary connection to things in themselves.

Kant deals very briefly with the idea of a God. In the Critique of Pure Reason, he shows at length the flaws in all the supposed proofs for the existence of God. Here, he simply points out that any "proof" of God's existence is a purely intellectual exercise, and cannot lead us to fundamental and substantial conclusions regarding the nature of experience.