Quidditism.

Abstract

In general, properties realize certain roles in the workings of nature. For example, mass makes objects resist acceleration. But what is the relationship between these roles and the properties that realize them? According to ‘quidditism’, the roles are contingently realized by the properties that in fact realize them. Opponents charge that quidditism implies the existence of epiphenomenal and unknowable “quiddities” or “inner natures”. The purpose of this dissertation is to argue in favor of quidditism and explore its epistemic and pragmatic consequences.

I begin by showing that certain considerations from physics show that properties cannot be individuated via their nomological roles, as anti-quidditism maintains. I then argue that quidditism can be had without epiphenomenal and unknowable quiddities. The arguments to the contrary proceed either from a misconception of what quidditism is, or they rely on an implicit assumption to the effect that quidditism implies that there is something in virtue of which properties are individuated from one another.

I turn next to an examination of quidditism’s epistemic implications. Here I develop and defend a posthumously published paper by David Lewis. Following Lewis, I argue that quidditism implies that we will never know which properties realize at least some of the nomological roles. At the core of my case is an argument against the common claim that quidditist skepticism is merely a species of traditional external-world skepticism.

Finally, having argued that quidditistic skepticism importantly differs from traditional external-world skepticism, I explore which, if either of these two types of skepticism have practical implications—that is, implications for how we ought to live our lives. I begin by getting clearer on the distinction between traditional external-world skepticism and quidditistic skepticism, showing that the former is of a kind I call ‘Cartesian skepticism’, while the latter is of a kind I call ‘Kantian skepticism’. A skepticism is Cartesian, on my terminology, if it posits ignorance of graspable facts; while it is Kantian if it posits ignorance of ungraspable facts. Finally, I argue that, in general, Cartesian skepticisms have drastic practical implications while Kantian skepticisms have none at all.