The study of responsibility is at the core of Westermarck’s ethics, being directly connected with his view on the retributive nature of moral emotions. Westermarck presents an extensive theory of moral responsibility based on his examination of conduct and character as the subject of moral judgements. Westermarck’s analysis of conduct covers human reactions towards acts, intentions, motives, the consequences and side-effects of action, and the different forms of negligence. In all these examinations, he explores the influence of chance on moral judgements, which contemporary philosophers call the phenomenon of moral luck. However, people are not praised or blamed only for what they do, but also for what they are. For this reason, following David Hume, Westermarck’s theory of moral responsibility is largely focused on the relationship between spectators’ moral emotions and the agent’s character. It covers also the question of what kind of agents deserve praise and blame, reward and punishment, and what kind of cognitive factors underlie these conceptions. Westermarck’s accounts of moral luck and moral agency are much influenced by Adam Smith. In Westermarck’s view, the regularities in the ways people make responsibility judgements cannot be understood without taking into account the retributive nature of the moral emotions. He was also very interested in how these emotional tendencies come to be reflected in criminal legislation. Thus, moral responsibility serves as an illustrative example of Westermarck’s general sociological approach, his attempt to make visible the emotional background of social institutions.