Sein and Sollen, “Is” and “Ought” and the Problem of Normativity in Hans Kelsen

Hans Kelsen’s Pure Theory of Law is a theory that seeks to draw a clear distinction between the object of study and the methods of inquiry within legal science. Its object of study is the knowledge of valid—i.e. existing—legal norms. Therefore, legal science according to Kelsen is a science that deals with the validity and not the efficacy of norms, and it is therefore a normative science, a science of the ought that is premised on the principle of imputation, which seeks to gain knowledge of and to describe the provisions that indicate the way in which people must behave and the sanctions that must be imposed on those who fail to act in the manner required. Legal science can, thus, be distinguished in terms of both its object and its method from other empirical and naturalist sciences, namely sciences based on the principle of causality. For Kelsen, validity is the prerequisite for the existence of positive law, the Sollen, while value is the foundation for natural law, the Sein.