In this chapter we will discuss some philosophical problems of theories of moral development, particularly those of Piaget, Kohlberg, and Gilligan. We will focus on their underlying assumptions about the moral domain. Therefore we will first introduce a rather broad concept of morality which may be helpful in elucidating the various aspects of morality implicit in these theories (horizontal analysis). It will become clear that the three theories cover only certain restricted aspects of morality. Next we compare and discuss the three approaches to the development of moral judgment (vertical reconstruction). Then we will go into two philosophical problems connected with these theories of moral development, namely the problem of the justification of moral principles and the problem of the relation between judgment and action.