This chapter discusses an overall interpretation of the Finnish sociologist, anthropologist and philosopher Edward Westermarck’s moral and social theory. Scholarship on Westermarck’s work on morality has been largely concerned with the moral-philosophical aspects and broader historical contexts of his thought. Westermarck grew up in a wealthy, academic Swedish-speaking family in Helsinki, the capital of the Grand Duchy of Finland, then an autonomous part of the Russian Empire. As an undergraduate at the Imperial Alexander University of Finland, he became much attracted to British empiricist philosophers such as Locke, Hume, Spencer and Mill and focused on psychology and philosophy. The portrayal of Westermarck presented focuses primarily on the structure and logic of his ideas and work. The Chapter discusses Westermarck’s view of the relationship between ethics and sociology and outlines the theoretical and methodological foundations of his work.