To answer this question, the book refers to three theories: theory of evolution, systems theory, and semiotics. Against this background, it traces the emergence of religion from general societal processes and the differentiation from its environment (other societal subsystems, mental systems, organic and physical conditions). It is shown how the religious system draws information from its environment and at the same time provides its environment with meanings. Applying the theories mentioned, four dimensions are distinguished in which religion evolves: experience, embodiment, cognition, and regulation. Overall, the approach understands religion as a specific sign system that deals with indeterminable contingency with the help of the distinction between known immanence and absolute transcendence. The book offers a way out of the false alternative of either following religious self-descriptions or explaining away religion and completely dissolving it into non-religious factors, such as political, economic, or mental circumstances.