This book is a defence of the thesis that free will and determinism are incompatible, and an exploration of some of the consequences of this thesis. Free will is understood at the power to act otherwise than one in fact does, and determinism is understood as the thesis that the past and the laws of nature together determine a unique future. The author argues that determinism is incompatible with free will because determinism entails that one’s present acts are determined by factors outside one’s control. Several arguments in favour of the compatibility of free will and determinism are examined and rejected, the most important being the argument that free will in fact entails determinism, since if one’s acts were undetermined by one’s past, they would be mere random occurrences. The author goes on to argue that moral responsibility requires free will; and that, since the reality of moral responsibility is not in doubt, and since there is no good reason to accept determinism, one should accept the existence of free will and reject determinism. The book also contains discussions of the problem of future contingencies, the paradigm-case argument, the thesis that ‘can’ statements are disguised conditionals, the relation between general laws and singular causal statements, the individuation of events, deliberation, and the nature of moral responsibility.