In the Anglo-American legal tradition, criminal guilt requires both that the defendant committed some forbidden action and that the defendant did it with intent, knowledge, or recklessness. The second requirement corresponds to the intuitive idea that people should not be punished for something that they did not do on purpose or if they did not realize what they were doing. However, this idea can be highly controversial in practice. The issues involved are examined in terms of their conceptual and moral foundations, including the Model Penal Code of the American Law Institute. In addition, the automatism and insanity defenses are considered with respect to the types of functional impairments experienced by typical defendants who use these defenses. The analysis concludes that the current approaches to these defenses are inadequate, in part because of the poorly articulated voluntary act and culpability requirements. A conceptual framework is proposed, based on philosophical action theory, to clarify the role of psychological processes in the structure-of-offense elements and to explain the nature of the voluntary act and culpability requirements and the relationship between the two. Footnotes and index