How to define rational behavior (practical rationality) is a philosophical problem of fundamental importance – both in its own right and by virtue of its close connection with the problem of theoretical rationality. The concept of rational behavior is equally fundamental to a number of more specialized disciplines: to normative disciplines such as decision theory (utility theory), game theory, and ethics; and to some positive Social sciences, such as economics and certain, more analytically oriented, versions of political science and of sociology.

This book presents what I believe to be the first systematic attempt to develop a conceptually clear, and quantitatively definite, general theory of rational behavior. No doubt, technically more advanced and philosophically more sophisticated versions of such a theory will soon follow. In fact, the first version of this book was completed in 1963, but game theory has been advancing at a very rapid rate since then, and my own thinking has also been changing. Thus, I have revised this manuscript several times to bring it more in line with new developments, but this process must stop if this material is ever to be published. I hope the reader will bear with me if he finds that this book does not cover some recent results, even some of my own. In such a rapidly growing subject as game theory, only journal articles – indeed, only research reports – can be really up to date.