The basic position of Otto in The Idea of the Holy2 may be stated as follows:

All religions involve and rest on experience of the numinous, which affords a positive knowledge of the central object of religion - God. This position is what may be called a Theory of Religion: like Freud's explanation of religion in terms of father figures, and Durkheim's claim that religion is society's celebration of itself, it claims to give an explanation of the phenomenon of religion - the fact that men belong to religions etc. Unlike some of its rivals, this Theory of Religion does not explain religion away; the explanation is intended to be compatible with religious belief; the explanatory concepts are supposed to be concepts from within religion. If Otto had just argued that religion was, or some religions were, true, his claims would have been only of theological interest. But what makes his writings especially important is that he looks at religion not merely as a theologian, but also as a phenomenologist; he is concerned to explain religion and religions as they are; even to explain the diversity of religions (with a version of evolutionism). It would be over-simple, but not entirely wide of the truth, to say that he first looks at religions in the sensitive but neutral manner of the phenomenologist, to decide what are the central phenomena of religion; and then puts forward a theological explanation of these phenomena. At least, this is what for much of his book he aims to do.