Kant on Self-Consciousness

The highest principle of Kant's theoretical philosophy is that all cognition must be combined in one single (A 117a, B 136).1 Elsewhere I have tried to explain why he believed that all cognition must belong to a single self (Kitcher 1982); here I try to clarify the other half of the doctrine. What led him to the claim that all cognition involved self-consciousness? This question is pressing, because the thesis strikes many as obviously false (for example, Bennett 1966, 105). My interpretive hypothesis begins from three clues. First, Kant characterized the self-consciousness at issue as transcendental (for example, B 132), meaning both that it is a necessary condition for the possibility of cognitive experience and that it involves factors not derived from the senses.2 (I mark this special usage with