This volume gathers twelve essays by David Wiggins in an area where his work has been particularly influential. Among the subjects treated are: persistence of a substance through change, the notion of a continuant, the logic of identity, the co-occupation of space by a continuant and its matter, the relation of person to human organism, the metaphysical idea of a person, the status of artefacts, the relation of the three-dimensional and four-dimensional conceptions of reality, and the nomological underpinning of sortal classification. From a much larger body of work the author has selected, edited or annotated, and variously shortened or extended eleven pieces. He has added an Introduction and one completely new essay, on the philosophy of biology and the role there of the idea of process. The collection begins with an essay postdating his Sameness and Substance Renewed (2001), which amends and upstages his earlier presentation of his sortalist conception of identity. In subsequent essays and the introduction Wiggins examines the contributions to these subjects made by Heraclitus, Aristotle, Leibniz, Roderick Chisholm, Hilary Putnam, Sydney Shoemaker, Michael Ayers, Saul Kripke, W. V. Quine, David Lewis, Fei Xu, and others.