Although Westermarck’s views on the origin and nature of morality underwent many changes before settling into their final form, many of the emotional and social tendencies that Westermarck discussed in his early work proved essential for his theory of moral emotions. These include the Darwinian evolutionary idea that the moral emotions are gradually moulded modifications of characteristics humans share with many animals. The same applies to sympathy, which is extensively explored in Westermarck’s work. In addition to sympathy, he should be recognised as a major theorist of reciprocity. In his study of morality, Westermarck explores the moral emotions and the mediating psychological mechanisms through which these emotions arise both from the proximate and ultimate evolutionary viewpoints. Despite his psychological and biological emphases, Westermarck does not deal with individual consciousness without the social context. One of the key merits of his moral theory is that it helps us to understand and explain various fundamental social phenomena that everyone may observe and recognise around them. Westermarck’s legacy serves as an example of sociological theory-building that is not organised around the dichotomies of nature and culture, or animal and human.