It is a well-known fact that Kant states that we cannot have full knowledge of ourselves qua noumena. However this is not all that he has to say concerning self-knowledge. He also claims that what makes knowledge of ourselves qua noumena impossible is also what makes other forms of self-knowledge possible, including some forms in which we achieve full certainty. In this paper I deal with these claims in order to analyze how this complex model is at work in Kant's practical philosophy.