Sentimental Rules is an ambitious and highly interdisciplinary work, which proposes and defends a new theory about the nature and evolution of moral judgment. In it, philosopher Shaun Nichols develops the theory that emotions play a critical role in both the psychological and the cultural underpinnings of basic moral judgment. Nichols argues that our norms prohibiting the harming of others are fundamentally associated with our emotional responses to those harms, and that such “sentimental rules” enjoy an advantage in cultural evolution, which partly explains the success of certain moral norms. This has sweeping and exciting implications for philosophical ethics. Nichols builds on an explosion of recent intriguing experimental work in psychology on our capacity for moral judgment and shows how this empirical work has broad import for enduring philosophical problems. The result is an account that illuminates fundamental questions about the character of moral emotions and the role of sentiment and reason in how we make our moral judgments. This work should appeal widely across philosophy and the other disciplines that comprise cognitive science.