The majority of the world’s cultures encourage or require members to enter alternative states of consciousness while involved in religious rituals. The question is, why? This paper suggests an explanation for the culturally prescribed ASC from the view of Fisher information. It argues from the position, first put forward by Emile Durkheim in his magnum opus, The Elementary Forms of the Religious Life, that all religions are grounded in reality. It suggests that many of the structural elements of cultural cosmologies (...) are similar and that the ritual induction of ASC may help to bring individual experience into greater accord with a pan-human eidetic cosmology, and thus with certain invariant attributes of reality. The necessity of this process is demonstrated by recourse to Fisher information. The paper shows how experiences generated during alternative states of consciousness may help to maintain a minimal level of realism in the interests of adaptation to what is in other respects a transcendental reality. (shrink)