This chapter attempts to answer the central objection that many philosophers will raise against the idea (which was defended in the previous chapter) that there are irreducible normative facts. According to a plausible naturalistic conception of the world, the natural facts in some sense determine the fundamental nature of the world. But how can this idea of irreducible normative facts be reconciled with such a naturalistic conception of the world? A modest form of naturalism implies only that all contingent facts are realized in (and so also supervene on) natural facts. It is argued here that this view can be reconciled with the thesis that there are irreducible normative facts and properties (although the reconciliation requires some far-reaching reflections on the nature of the concepts of ‘essence’ and ‘metaphysical necessity’, and even on the question of which is the right modal logic for metaphysical necessity).
Keywords: irreducibility, normative facts, naturalism, realization, supervenience, essence, metaphysical necessity, modal logic