Normative Objectivity Without Ontological Commitments?

Several non-naturalist philosophers look for ways to maintain the objectivity of morals without making any (robust) ontological commitments. Recently Derek Parfit proposed an account of non-ontologically existing irreducible moral properties. My first aim in this paper is to outline that such an account is doomed to fail. My second aim in this paper is to argue that irreducible moral properties can be integrated with adaptions into an ontological framework such as E.J. Lowe's four-category ontology. If it can be shown that irreducible moral properties have a proper place in such an ontology, then there is no need to distinguish between an ontological and non-ontological mode of existence, which, in turn helps to eschew the obscurities that this distinction brings in its wake.