This article presents the main theoretical approaches to the religious phenomenon: functionalism, constructivism, civil religion, invisible religion, diffused religion, rational choice, vicarious religion, and so on. It is difficult to accumulate empirical data that in general are considered too weak. The state of the art of sociology of religion seems promising because of the presence of new generations of sociologists who are deeply involved in their work. For the future a specific theory on migration mobility is necessary. Another necessity is (...) a wider development of qualitative analysis for a better knowledge of religious dynamics. (shrink)