Luban’s new monograph is a ‘book about conscience and moral clarity’, asking how some keep their moral judgment ‘steadfast even when multitudes around them are swept away’ by totalitarianism or war. He blends Arendt’s arguments with contemporary concerns of moral philosophers and international criminal justice jurists. She became interested in moral judgment in emergencies through the 1961 Eichmann trial in Jerusalem, the book’s gateway (Chapters 1–2) to the thinking-judging connection (Chapters 3–5), contemporary collapse of common sense (Chapters 6–7), an ‘amoralist outlook’ in her early writings (Chapters 8–9), and Arendt and international law (Chapters 10–15). For her, crimes against humanity are crimes against all humankind; characterised, for Luban, by our political institutions turning on us (‘politics gone cancerous’). Building on Arendt, Luban posits the ‘idea of humanity’ as the ‘fellowship recognized by those committed, for various reasons, to a cross-border project of responsibility’. This ‘project of constructing humanity’ is international law’s ‘regulating ideal’. He discusses how courts can be paradigms or ‘institutional embodiments of spectator judgment’. He explains why expressive and history-preserving aims of atrocity trials affirm Arendt’s injunction that ‘men must assume responsibility for all crimes committed by men’ and spends six pages refuting Koskenniemi’s critique of such trials. On some questions Luban makes better sense of Arendt than she may herself have done, while spelling out his disagreement with her on other points. Luban’s new monograph is one of the most insightful books published on theory of international criminal law. Himself a philosopher, the book is legalese-free and – written over a period of ten years – it reads unusually well (‘orthodox international law is addicted to the paraphernalia of sovereignty’).