Description:This book is a study of John Locke's metaphysics of organisms and persons, with particular emphasis on his theory of identity through time and his conventionalism with respect to kinds and essences. After presenting three arguments for thinking that the organisms and persons in Locke's ontology have both spatial and temporal extent, the author argues that on a four-dimensional ontology there is no contradiction between Locke's theory of identity and his rejection of essentialism.