Kant's philosophy of critique responds to four questions: what can I know, what should I do, what may I hope and what is man. The first three are on I-first person, but the last is on a universal man, or cosmopolitan. These seem to belong to different realms with diverse meanings. But in effect, "what can I know" possesses a fundamental position and function. Given a philosophical interpretation on relationship between the first question and epoche of ontology, it is helpful with our comprehension of Kant's efforts to seek balance between individual concerns and public welfare, individual freedom and public domain.