In this book, which thoroughly revises and greatly expands his classic work Sameness and Substance (1980), David Wiggins retrieves and refurbishes in the light of twentieth-century logic and logical theory certain conceptions of identity, of substance and of persistence through change that philosophy inherits from its past. In this new version, he vindicates the absoluteness, necessity, determinateness and all or nothing character of identity against rival conceptions. He defends a form of essentialism that he calls individuative essentialism, and then a form of realism that he calls conceptualist realism, a position he seeks to place in relation to one surviving insight of idealism. In a final chapter, he advocates a human being based conception of the identity and individuation of persons, arguing that any satisfactory account of personal memory must enforce and follow through all the normative requirements that flow from its logically inalienable aspiration to furnish direct knowledge of the rememberer's own past. This important book will appeal to a wide range of readers in metaphysics, philosophical logic, and analytical philosophy.