Religion describes the beliefs, values, and practices related to sacred or spiritual concerns. Social theorist Émile Durkheim defined religion as a “unified system of beliefs and practices relative to sacred things” (1915). Max Weber believed religion could be a force for social change. Karl Marx viewed religion as a tool used by capitalist societies to perpetuate inequality. Religion is a social institution, because it includes beliefs and practices that serve the needs of society. Religion is also an example of a cultural universal, because it is found in all societies in one form or another. Functionalism, conflict theory, and interactionism all provide valuable ways for sociologists to understand religion.