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.