This book reviews the psycho-physiological and other studies on the effects of Transcendental Meditation (TM) and concludes that the largely positive effects justify the use of TM as a form of Psychotherapy. Adopting TM as a form of psychotherapy, however, calls for an adoption of its underlying spiritual psychology which, in turn, implies the adoption of an underlying paradigm very different and contrary to the paradigms of psychoanalytic, behaviouristic and humanistic psychotherapies. Two “underworlds” seem to clash. The spiritual psychology of TM is described and the differing assumptions are contrasted. Some signs of this paradigm shift already occurring in American Society, even at academic levels are pointed out.