All social theorists and philosophers who seek to explain human action have a 'model of man'; a metaphysical view of human nature that requires its own theory of scientific knowledge. In this influential book, Martin Hollis examines the tensions that arise from the differing views of sociologists, economists and psychologists. He then develops a rationalist model of his own which connects personal and social identity through a theory of rational action and a priori knowledge, allowing humans to both act freely and still be a subject for scientific explanation. Presented in a fresh series livery and including a specially commissioned preface written by Geoffrey Hawthorn, Hollis's important work is made available to a new generation of readers.