This is an examination of the problems of criminal liability through an analysis of provocation and related criminal defences. It begins by identifying fundamental questions about the function of partial defences in the criminal law as they emerge from a discussion of leading cases and statutory provisions and in the work of criminal law theorists. The relation between provocation and criminal liability is then subjected to theoretical scrutiny, with particular emphasis on the moral distinction between justification and excuse, and the implications of different theoretical approaches to the defence are examined in a number of related issues. These include the role and limitations of the objective - or ""reasonable person"" - test, the principle of proportionality, the problem of impaired volition and the possible connection between provocation and other defences, especially self-defence and diminished responsibility.;Although the analysis focuses on the defence of provocation as it operates in English law, the perspective to other legal systems which are included in the work add an important comparative perspective to the discussion of the issues.