This volume of essays is very much a sequel to the two earlier collections by Jon Elster, Ulysses and the Sirens and Sour Grapes. His topic is rationality - its scope, its limitations, and its failures. Elster considers rational responses to the insufficiency of reason itself, and to the ‘indeterminacies’ in deploying rational-choice theory and discusses the irrationality of not seeing when, where, and what these are. A key essay which gives the collection its title examines disputes in cases of child custody, which are paradigmatically indeterminate. Leaving aside cases where one parent is patently unfit and assuming that protracted dispute is against the immediate interests of the child, Elster argues that three options present themselves: a strong presumption in favour of the mother, a strong presumption in favour of the primary caretaker (also likely to be the mother), and tossing a coin. Though the first two options may be preferable in the short/medium term, Elster argues that there is a case for randomisation in the long term. The book will be read with interest by anyone concerned with political and social science.