Abstract
This paper examines the import of the is-ought dichotomy in Kelsen's theory of norms. The argument starts with the thesis that the separation of is and ought as a logical criterion for the scientific theory of norms requires not only that ‘norms are not to be derived from facts’, but also that ‘facts are not to be derived from norms’. Kelsen’s reasoning to meet the first condition is explained by an analysis of his critique on the ontologico-ethical justification of norms. Kelsen’s alternative, formal justification via the concept of the basic norm is presented and evaluated. The way in which Kelsen meets the second condition of the criterion is shown in an analysis of his critique on the common sense conception of the practical meaning of norms. Kelsen’s alternative interpretation via the concept of the modally indifferent substratum is explained and questioned. The argument enables to conclude that, contrary to the received view, Kelsen’s theory of norms does not reflect moral relativism but unmitigated moral scepticism