Maxims do not merely express what kind of a person one is; they constitute that person, in some sense. They constitute the person as character. In other words, to have a certain set of maxims and to have character (or to be a person) is one and the same thing. This is perhaps the most important point of Kant’s anthropological discussion of maxims. Maxims are character-constituting principles. They make us who we are, and without them we are, at least according to Kant, nobody.
Manfred Kuehn, Kant: A Biography, Cambridge, 2001, p. 146