Quidditism without quiddities

Abstract

Structuralism and quidditism are competing views of the metaphysics of property individuation: structuralists claim that properties are individuated by their nomological roles; quidditists claim that they are individuated by something else. This paper (1) refutes what many see as the best reason to accept structuralism over quidditism and (2) offers a methodological argument in favor of a quidditism. The standard charge against quidditism is that it commits us to something ontologically otiose: intrinsic aspects of properties, so-called ‘quiddities’. Here I grant that quiddities are ontologically otiose, but deny that quidditism requires them. According to a view I call ‘austere quidditism’, properties are individuated by bare numerical identity. I argue that, as far as ontological parsimony is concerned, austere quidditism and structuralism are on a par. But is austere quidditism a coherent alternative to structuralism? To see that it is, we must get clear on what exactly we mean by ‘property individuation’. What we discover is that structuralism is a counterpart theory for properties, and that austere quidditism is simply the rejection of counterpart theory. I conclude with a methodological argument to the effect that counterpart theory for properties ought to be rejected. This paper begins by situating the debate between structuralists and quidditists within the context of a debate over the epistemic limits of fundamental science. At the center of this debate is David Lewis’s posthumously published ‘Ramseyan Humility’ (2008). In the appendix I explain the precise role of austere quidditism in Lewis’s argument.