This book didn’t have to consist of exactly the sentences that it in fact contains: any one of its sentences could have been very different. But it could not have consisted of an entirely different collection of sentences, such as to make it a gothic novel or a treatise on wine-tasting. Other familiar objects are similarly capable of being moderately different, but not radically different, in various respects. But there are puzzling arguments which threaten these apparently obvious judgments, exploiting the fact that an appropriate sequence of small differences can add up to a radical difference. This book presents the first full-length treatment of these puzzles, using them as an entry point to a broad range of metaphysical questions about possibility, necessity, and identity. It introduces tools of higher-order modal logic which enable a rigorous treatment of the puzzles, and develops a strategy for resolving them based on a plenitudinous ontology of material objects, which induces fine-grained variability in the reference of words like ‘book’
