With ontology motivated largely by causal considerations, this lucid and provocative work focuses on the idea that physical objects are causally non-redundant. Merricks "eliminates" inanimate composite macrophysical objects on the grounds that they would--if they existed--be at best completely causally redundant. He defends human existence by arguing, from certain facts about mental causation, that we cause things that are not determined by our proper parts. He also provides insight into a variety of philosophical puzzles, while addressing many significant issues like free will, the "reduction" of a composite object to its parts, and the ways in which identity over time can "for practical purposes" be a matter of convention. Anyone working in metaphysics will enjoy this book immensely.