In this paper I highlight some of the problems of the Kelsenian conception of legal interpretation. The analysis has two main theses. The first maintains that Kelsen has no unitary concept of legal interpretation because with these words he would refer to very different activities which cannot be gathered in a unitary understanding. The second thesis – not completely independent from the former – is that Kelsen would not even have a unitary concept of the indefiniteness of Law. Finally, I try to offer an explanation for this deficient portrayal of interpretation given its central position for the understanding of Law. This explanation is based on Kelsenian moral skepticism, which also lies at the centre of his claim of the purity of a legal theory.