THE EXPERIENCES resulting from the use of psychedelic drugs are often described in religious terms. They are therefore of interest to those like myself who, in the tradition of William James, are concerned with the psychology of religion. For more than thirty years I have been studying the causes, the consequences, and the conditions of those peculiar state consciousness in which the individual discovers himself to be one continuous process with God, with the Universe, with the Ground of Being, of whatever name he may use by cultural conditioning or personal preference for the ultimate and eternal reality. We have no satisfactory and definitive name for experiences of this kind. The terms “religious experience,” “mystical experience,” and “cosmic consciousness” are all too vague and comprehensive to denote that specific mode of consciousness which, to those who have known it, is as real and overwhelming as falling in love. This Article describes such states of consciousness as and when induced by psychedelic drugs, although they are virtually indistinguishable from genuine mystical experience. The Article then discusses objections to the use of psychedelic drugs which arise mainly from the opposition between mystical values and the traditional religious and secular values of Western society.