Philosophical theories of agency and responsibility have focused primarily on actions and activities. But, besides acting, we often omit to do or refrain from doing certain things. Omitting or refraining, like acting, can have consequences, good and bad. And we can be praiseworthy or blameworthy for omitting or refraining. However, omitting and refraining are not simply special cases of action; they require their own distinctive treatment. In Omissions, Randolph Clarke offers the first comprehensive account of these phenomena, addressing three main questions: What is an omission? What is it to intentionally not do a certain thing? And what does it take to be morally responsible for omitting or refraining? Clarke examines the connection between negligence and omission, the distinction between doing and allowing, and the distinction in law between act and omission. With its attention to a previously neglected topic, Omissions broadens our understanding of human agency.