This book is a philosophers' attempt to bring together ideas put forward by economists, sociologists and political theorists. The author begins by exploring the economist's assumption that action is rational if it helps to achieve the agent's goals as efficiently as possible. The assumption is explored with the aid of rational-choice theory and game-theory, but it is rejected in the end for failing to account for the elements of trust and morality which rational social life requires. A discussion of 'Rational Expectations' and of 'maximising' and 'satisficing' leads to a portrait of social actors as rational role-players. Rationality is, finally, the expression of the self in a social world. The book intervenes in intense current debates within and among several disciplines. Its concern is with the true nature of social actors and the proper character of social science. Its arguments are the more challenging for being presented in a simple, incisive and lucid prose. It will be of particular interest to philosophers, social theorists and social scientists interested in the philosophical aspects of their discipline.