The capacity for the mystical experience has important evolutionary and psychodynamic implications. Most readers of this journal are going to want to know if a book about this subject is practical, relevant, and sufficiently comprehensive to be helpful in the practice of psychiatry. From my review, the reader will have no misunderstanding of what this book is about. Very few readers will feel a need to know about the more parochial and esoteric aspects of this subject. A basic fault with Ostow's book is expressed, paradoxically enough, in the sentence he cites, the last sentence of his book. The sentence begins, "Many of us who cannot accept the non-rational assumptions necessary to embrace mysticism" and ends with a little sop for the benighted ones, the "millions" who, through the centuries, have, by implication, abandoned rationality in their search for progressive solace. Such a perspective, i.e., that mysticism is "non-rational," precludes alternative psychoanalytic explanations. Thus, the idea that mysticism is an example of experience in the progressive transitional mode (1–3) is not even considered by Ostow and his colleagues.