According to Michael Devitt, the primary work of a rigidity distinction for kind terms is to distinguish non-descriptional predicates from descriptional predicates. The standard conception of rigidity fails to do this work when it is extended to kind terms. Against the standard conception, Devitt defends rigid application: a predicate is a rigid applier iff, if it applies to an object in one world, it applies to that object in every world in which it exists. Devitt maintains that rigid application does (...) the job of identifying nondescriptional predicates perfectly. I argue that Devitt is wrong about this. When we examine more closely alternative theories about the identity and persistence conditions of those entities to which mass terms apply, we find no plausible theory that has the result that a term is rigid iff it is non-descriptional. (shrink)

In this article, I show that the semantics one adopts for mass terms constrains the metaphysical claims one can make about mixtures. I first expose why mixtures challenge a singularist approach based on mereological sums. After discussing an alternative, non-singularist approach, I take chemistry into account and explain how it changes our perspective on these issues.

A view of individuals as constituted of quantities of matter, both understood as continuants enduring over time, is elaborated in some detail. Constitution is a three-place relation which can't be collapsed to identity because of the place-holder for a time and because individuals and quantities of matter have such a radically different character. Individuals are transient entities with limited lifetimes, whereas quantities are permanent existents undergoing change in physical and chemical properties from time to time. Coincidence, considered as a matter (...) of occupying the same place, is developed, alongside sameness of constitutive matter, as a criterion of identity for individuals. Quantities satisfy the mereological criterion of identity, applicable to entities subject to mereological relations and operations such as regions of space and intervals of time. A time-dependent analogue of mereological parthood is defined for individuals, in terms of which analogues of the other mereological relations can be defined. But it is argued that there is no analogue of the mereological operation of summation for individuals. (shrink)

Anyone who admits the existence of composite objects allows a certain kind of coincidence, coincidence of a thing with its parts. I argue here that a similar sort of coincidence, coincidence of a thing with the stuff that constitutes it, should be equally acceptable. Acknowledgement of this is enough to solve the traditional problem of the coincidence of a statue and the clay or bronze it is made of. In support of this, I offer some principles for the persistence of (...) stuff that are general, not relying on the particular features of a kind of stuff in the way that principles for the persistence for a thing would. This provides a non-arbitrary grounding for stuff that is independent of the conditions on the nature and persistence of things the stuff composes. The principles also provide a general basis for responding to other questions about coincident stuff. (shrink)

Mereological essentialists argue that mereological summations cannot change their parts. Mereological inessentialists argue that mereological summations can change some or all of their parts. In this paper I articulate and defend a position called Moderate Mereological Inessentialism, according to which certain mereological summations can change some, but not all, of their parts. Persistent mereological summations occur when the functional parts of mereological summations persist through alterations to its spatial parts.

An overview of contemporary part-whole theories, with reference to both their axiomatic developments and their philosophical underpinnings.