This thesis examines some of the philosophical problems which underlie the cognitive-developmental approach to morality as it has been presented in the Piaget-Kohlberg theory. This theory of moralization is reviewed, synthesized and evaluated in order to demonstrate the substantial body of empirical research on which it is founded and to focus on some of the unresolved theoretical issues and methodological problems such as stage generality, motivation, decalage and cross-cultural validity. The problem of explanation is discussed in relation to the appropriateness of alternative modes and it is concluded that, as cognitive-developmentalism is a theory of human action, it requires an explanatory paradigm which takes cognizance of (i) the agent's viewpoint and reasons for acting, (ii) a molar level of behavioural analysis, (iii) enabling conditions for choice, and (iv) cognitive processes of appraisal and judgment. The assumptions underlying the cognitive-developmental explanation of moral judgment are examined in relation to the proposed paradigm. It is contended that the concept of judgment, which is central to the theory, is not adequately defined and its logical status within the practical reasoning process is not explicated within the cognitive-developmental theory. The prescriptivism which is assumed by the theory does not explain the logical connection between reasons for action and the universalizable imperative; nor does it adequately account for discrepancies between judgment and action. Kohlberg's approach to morality lies within the Kantian tradition but even within this context his theory entails a number of metaethical problems. In the present thesis, it is argued that the theory provides no adequate criteria for defining the moral domain and that its claim for formal universality of moral principles cannot be supported. Kohlberg's moral position is inconsistent and shifts between formal prescriptivism and a naturalistic claim for the place of justice as the supreme moral principle. The problem of justification for moral principles is evaded. By emphasizing the cognitive aspects of moral judgment and the place of prescriptive principles at the highest stage, the theory neglects the effective and motivational features of morality and the influence of beliefs, habits and personal ideals on moral conduct. It is argued that Kohlberg's claim for the isomorphism of psychological and normative structure cannot be supported and his argument for the solution of the is/ought problem remains untenable. Finally, Kohlberg's developmentalist ideology is discussed with special reference to educational implications. It is argued that there is a sufficiency fallacy in cognitive-developmentalism and that the theory is equivocal in its employment of the concepts of rationality and autonomy. An attempt is made to define these concepts in relation to development and education in order to illustrate the limitations of Kohlberg's concept of 'cognitive stimulation' and his advocacy of 'development' as an aim for education. The importance of Kohlberg's theory is not disputed in this thesis but it is argued that he claims too much for it in relation to the philosophical problems which it entails and the relevance to moral education which it implies.