The problem of acting against one's better judgement is known as weak-willed or irrational behaviour. It perplexed Socrates, Plato and Aristotle and has been the subject of keen debate by recent philosophers - partly as a result of work by Hare, Anscombe and Davidson. This book is intended as a comprehensive introduction to both ancient and modern discussions. Two chapters cover the work of Socrates, Plato and Aristotle. A further four central chapters deal with modern ideas about volition, trying and intention, with modern analyses of what it is to think something good, and with the debates provoked by R.M. Hare and Donald Davidson. Two further chapters examine selected explanations of weak-willed behaviour in the light of recent work in psychology. Among different explanations of weak-willed behaviour William Charlton considers compulsive desires, unconscious motivations and various kinds of intellectual failure. He discusses proposals by Plato, Freud and Davidson for partitioning the psyche and offers his own teleological view of human conduct as explainable in terms of reasons and purposes. In conclusion he compares the different approaches to the topic by the philosopher, psychologist and the economic theorist. This work is aimed at students of philosophy in the second year and above.