Over his philosophical career, David Wiggins has produced a body of work that, though varied and wide-ranging, stands as a coherent and carefully integrated whole. In this book Ferner examines Wiggins’ conceptualist-realism, his sortal theory ‘D’ and his human being theory in order to assess how far these elements of his systematic metaphysics connect. In addition to rectifying misinterpretations and analysing the relations between Wiggins’ works, Ferner reveals the importance of the philosophy of biology to Wiggins’ approach. This book elucidates the biological anti-reductionism present in Wiggins’ work and highlights how this stance stands as a productive alternative to emergentism. With an analysis of Wiggins’ construal of substances, specifically organisms, the book goes on to discuss how Wiggins brings together the concept of a person with the concept of a natural substance, or human being. An extensive introduction to the work of David Wiggins, as well as a contribution to the dialogue between personal identity theorists and philosophers of biology, this book will appeal to students and scholars working in the areas of philosophy, biology and the history of Anglophone metaphysics.