Sympathy has many distinct but related functions in Westermarck’s moral and social theory. Besides explaining how the moral emotions arise, sympathy plays a key role in Westermarck’s account of the evolutionary origins of human emotional and social bonds. However, unlike Durkheim and others have assumed, Westermarck was not trying to explain human marriage practices solely in terms of psychological and biological causes. In addition to family and kin relationships, sympathy contributes to the emergence of human society in a broader sense, which is linked to Westermarck’s theory of the evolution of moral emotions. A key part of Westermarck’s position is that the expanding circle of sympathy can be explained in terms of evolution by natural selection only up to the level of early foraging societies. After this, the expansion of the moral community results from the growth in the size of social units and the increase of peaceful, cooperative interactions between different human groups. There are, however, several factors that continue to narrow the sphere of sympathy between human communities and between social groups within larger societies. Because the range of sympathy determines the limits of moral community, these variations also lead to the deviating occurrences of moral emotions.