An action is the outcome of a choice within constraints. The choice, according to the orthodox view, embodies an element of freedom, the constraints one of necessity. In non-standard cases, however, these equations do not hold. The title of an earlier book on rational and irrational behaviour, Ulysses and the Sirens, is a reminder that men sometimes are free to choose their own constraints. Sour Grapes conversely reflects the idea that the preferences underlying a choice may be shaped by the constraints. Considered together, these two non-standard phenomena are sufficiently important to suggest that the orthodox theory is due for fundamental revision.

The present book, then, supplements my earlier work. To some extent it also corrects what I now see as an overly enthusiastic application of the idea that men can choose their own character. The chapter on states that are essentially by-products suggests that there are limits to what may be achieved by character planning. There is hubris in the view that one can be the master of one's soul – just as there is an intellectual fallacy in the view that everything that comes about by action can also be brought about by action.

The book is also an attempt to spell out some strands in the complex notions of rationality, intentionality and optimality. Some of the issues raised in this connection are more fully discussed in my Explaining Technical Change. This holds in particular for the analysis of functional explanation.

My first acknowledgement is to G. A. Cohen, who has commented extensively and intensively on successive drafts of Chapters II, III and IV. Without his ability to force me out of a congenital intellectual laziness, the level of argument would have been much lower. Next, I want to thank the members of a Working Group on Rationality, set up under the auspices of the Maison des Sciences de l'Homme, for helpful discussion and constant inspiration. In particular my gratitude goes to Brian Barry, Donald Davidson, Dagfinn Føllesdal, Robert Goodin, Serge Kolm, Amélie Rorty, Amos Tversky and Bernard Williams. Finally I should mention what will be obvious to any reader – my immense intellectual debt to the outstanding work by Paul Veyne, Le Pain et le Cirque.