Dean Zimmerman

This book addresses two basic questions: What is the proper philosophical analysis of the concept of substance? and What kinds of compound substances are there? The second question is mainly addressed by asking what relations among objects are necessary and sufficient for their coming to compose a larger whole. The first 72 pages of the book contain a short history of attempts to answer the first question, and a brief presentation of the analysis the authors defend at length in their earlier book, Substance Among Other Categories. In the remaining 119 pages, the authors take up the second question. This order of presentation makes sense; but it may help to create a false impression in those who only glance at the first few pages—that this book is just a simplified version of the earlier one, with a little bit of history thrown in. It would be quite unfortunate, however, if very many potential readers get this impression; for it might discourage them from looking closely at the bulk of the book, which is new. The issues discussed in the later chapters are at the center of one of the most lively debates in contemporary metaphysics; and the position Hoffman and Rosenkrantz stake out is appealing and carefully articulated. Their views deserve careful attention from philosophers working on the metaphysics of persistence through time, personal identity, artifact identity, and mereology.

The ‘friends of temporal parts’ and their opponents disagree about how things persist through time. The former, who hold what is sometimes called a ‘4D’ theory of persistence, typically claim that all objects that last for any period of time are spread out through time in the same way that spatially extended objects are spread out through space — a different part for each region that the object fills. David Lewis calls this manner of persisting ‘perdurance’. The opposing, ‘3D’ theory has it that at least some objects do not persist in this manner; they ‘endure’ through time by ‘being wholly present at more than one time’.1 A related dispute pits ‘presentists’ against ‘non-presentists’. Presentists hold that the only things that really exist are those that exist now, at the present moment; and nonpresentists believe in something like a ‘block-universe’ in which non-simultaneous objects and events nevertheless co-exist (in a tenseless or non-temporal sense). Of late, the relations between these four positions have come under considerable scrutiny.2 As Ned Markosian has pointed out, it would be surprising if commitment to a perdurance or endurance theory of persistence automatically foreclosed one’s options in the presentism—non-presentism debate. But, says Markosian, that is just what the standard formulations of the perdurance and endurance theories imply.3 David Lewis has set the terms of the debate; in his usage, someone who thinks that all persisting objects endure would be said to hold the following.