To act or not to act. To intervene or stand aside. Are these only moral questions, or should they also be legal ones? They arise when a doctor withdraws treatment, when a passer-by fails to help someone in danger and increasingly, when machines are designed to make choices on our behalf. As autonomous systems become more common and societies grapple with issues of ageing populations and end-of-life care, the line between doing harm and allowing harm to occur is likely to become even more controversial. Dr Roni Rosenberg’s Act and Omission in Criminal Law: Autonomy, Morality and Applications to Euthanasia takes this long-standing problem as its starting point. Despite what the title suggests, the book is not only about euthanasia. Its central concern is a deeper question about the distinction between acts and omissions and what justifies that distinction. At the heart of the analysis, Rosenberg considers the relevance of identifying a duty to act as an anchor for justifying criminal liability in omissions.