“Ignorance of the law is no excuse” is a venerable legal maxim, one that is well known among laypeople as well as lawyers. It is mentioned by Aristotle and observed, with few qualifications, in Roman as well as common- law systems. But is it a good principle? As the number and technicality of statutory offenses continues to grow in most countries, the ability of people, even lawyers, to have a good command of what the law requires of them declines. Douglas Husak is inspired by this worrying aspect of contemporary life to offer a wide- ranging re- evaluation of the old maxim, exposing its troubling presuppositions and implications with characteristic wit and style as well as rigor and insight. In the process he introduces us to many interrelated and crosscutting themes that no other author has brought together. The book opens up numerous avenues of further exploration for the reader, and luminously explains the relations among them. The work is a major contribution to the study of legal and moral responsibility more widely, and not only a searing critique of received legal wisdom on the subject of how to deal with understandable ignorance.