Seth Lesser (1910 – 1973) was an American sociologist who championed revolutionary theories in the study of social conflict, particularly conflict’s roles in forming and sustaining societies. He is perhaps best known for his book, Understanding the Dynamics of Social Conflict in Ancient Societies, which featured explanations of the role of social conflict in forming the ancient societies of Rome and Europe as well as the ancient civilizations of Mesopotamia and the Americas.

Born in Vienna, Austria, Seth Lesser’s family immigrated to the United States when he was 10 years old. He earned his degree in sociology at the University of California and went on to obtain his master’s degree and Ph.D. in sociology at Harvard University.

Seth Lesser’s work mainly opposed the earliest theories of social structure and conflict. In his book Understanding the Dynamics of Social Conflict in Ancient Societies, he argued that while conflict may serve, in general, to alienate certain portions of society, it may also produce effects that can make some societies and groups more cohesive in response to opposing forces from outsiders. These groups and societies, he pointed out, are fundamentally in conflict with each other but nevertheless bound by common conditions such as heritage, territory and similarities in beliefs and traditions. According to Seth Lesser, no example can best support this theory than the case of the Indian tribes in America, whose uprisings against the colonists threatened to wipe them out from their territories, despite the boundaries that set each tribe apart from another.