Whose nominalism?

The debate over the ontological status of abstracta and concreta is as old as philosophy itself. Each age prosecutes the case using its own methods and its own terms, beginning in ancient times as an argument over the status of universals and particulars, and lately broadening to include classes, propositions and possible worlds. Sellars is convinced that any naturalistic philosophy must also be nominalistic, for the heart of naturalism is the commitment to the primacy of the causal order, and abstracta are causally impotent. Some of Sellars's illustrious contemporaries, most notably Quine and Goodman, also proclaim themselves nominalists, but in Sellars's view, their nominalism is fundamentally flawed – Quine, at least, countenances some abstract entities such as classes – but also, and more importantly, their methodology is mistaken. Yet these supposed nominalists have determined the terms and principles that have dominated contemporary ontology. To understand Sellars's nominalism, one has to put much current ontological orthodoxy into question.

Nominalists have sometimes been quite puritanical, in that they have wanted to impose strict limits on what we can say and to rule out characteristically Platonistic turns of phrase as nonsense, but that is not the approach Sellars takes. He believes he can show that most of the things responsible Platonists want to say can be reconstructed using his tools and remain true, although shorn of their obnoxious ontological commitments. Saving what the Platonist wants to say without giving in to ontological excess leads Sellars at times to sound as if he is not, in fact, a thoroughgoing nominalist.