Hans Kelsen's vast body of work is perhaps one of the best examples of the unremarkable but important point that one's legal theory and methodological choices are intricately tied up with how one understands international law. Kelsen stands for a huge number of different positions, but chief amongst them must be his insistence on developing a ‘pure’ theory of law that accounted for the unique normativity of law, separate from empirical facts and causality on the one hand, and substantive theories of justice on the other. For Kelsen, the unique normativity of law is found within the legal system itself, in the idea of normative imputation – the ‘linking of a conditioning material fact with a conditioned consequence’. According to Kelsen, this specifically legal sense of ‘ought’ is an a priori category that allows us to correctly cognize the legal meaning of empirical data.
