I aim to show that there are cases in which an ordinary material object exists intermittently. Afterwards there are a few words about the consequences of acknowledging such cases, but what is of more interest is the route by which the conclusion is reached. When deciding among competing descriptions of the cases considered, I have tried to reduce to a minimum the role of intuitive judgment, and I have based several arguments on "metaphysical principles," two of which I have defended.

A thorough critique (extracted from the author’s 1979 doctoral dissertation) of Kripke’s purported derivation, in footnote 56 of his philosophical masterpiece /Naming and Necessity/, of nontrivial modal essentialism from the theory of rigid designation.

The views of Quine and Strawson on the significance of 'mass terms' are rehearsed, and the metaphysical status of substances, in the chemist's sense, is considered. It is urged that the ontological dichotomy of particulars and universals is not adequate to accommodate such substances, which are in a sense to be explicated concrete but non-particular.