Kant's clarification of "I think, therefore I am."

In Section 25 of Deduction (B), Kant is clearly talking about the Cartesian Cogito, or, "I think, therefore I am." He deals with it right after discussing the nature of inner sense, and I believe that he sheds some much-needed light on the limitations of Descartes' famous phrase.

To quickly restate Kant's theory(?) of knowledge, the understanding must combine an intuition and a concept of the same object under a unified self-consciousness. This knowledge is only of appearances, and does not extend to the thing-in-itself, which would require some kind of intellectual intuition combined with a concept, and Kant admits that he does not know if we can have any intuition besides a sensible one.

From here, Kant takes the "I think" and renders it as a concept of our existence. Yet it is still a concept, and needs an intuition in order to become knowledge. Here, Kant makes use of "inner sense." It is by inner sense that we have an intuition of ourselves as an object of which we can have knowledge. The inner intuition that we have combines with our concept of "I think," and allows us to know that we do, in fact, exist. However, we do not exist any more so than other objects that we experience externally. We do not have some sort of special intellectual intuition that allows us to know ourselves as us-in-ourselves.

There are two (and possibly more) ways to view Descartes' Cogito. If one takes it as the starting point that Descartes uses to deduce everything else that follows in his Discourse, then it is plain that, in light of Kant, we cannot deduce things like God or the Soul from a knowledge that is only of appearances. However, one can also see the Cogito serves only as an example of a "clear and distinct" idea that Descartes is searching for so vehemently. While I believe Kant would agree that, while ambiguous in certain terms (The "I" of "I think," for example), it is clear that thinking implies existence of some sort, and that this idea is clear and distinct. But unless Descartes can provide some sort of intuition to accompany this idea, it will remain just an idea, and never knowledge.