A comparison is made between pure unitary consciousness as described by Walter Stace and transcendental consciousness as proposed by Maharishi Mahesh Yogi. The validity and authenticity of this state is investigated through the study of parallels between the Vedic description of reality and the viewpoints of recently postulated grand unified field theories, as well as a study of the physiological correlates, and psychological and sociological effects of the practice of the Transcendental Meditation (TM) and TM-Sidhi program. An empirical study is presented which compared 102 subjects with three levels of experience of the TM and TM-Sidhi program on a phenomenological experience questionnaire developed on basis of Stace's criteria of the "introvertive mystical experience." The findings substantiate the proposed identity of transcendental consciousness and pure unitary consciousness, and indicate that practitioners of the Transcendental Meditation and TM-Sidhi program have experiences that are identical to the historical descriptions of higher states of consciousness.