P. D. Ouspensky was one of the outstanding thinkers of the 20th century. he became convinced at a very early age of the existence of dimensions of reality beyond those which sufficed for the ordinary purposes of life, and he began to express his ideas in articles and books which soon gained for him a reputation for originality of thought. He travelled extensively in a search for the basic truths preserved in ancient legend, which he later interpreted in two major philosophical works, one of which 'A New Model of the Universe' brought him world-wide acclaim. In 1915 he met the Caucasian mystic G. I. Gurdjieff, who had brought from an Eastern monastery a system of ideas which Ouspensky immediately recognised as providing the key which he had so long sought. He devoted the rest of his life to the promulgation of these ideas by both public and private lectures and much later wrote a formulation of the system called 'In Search of the Miraculous' which is recognised as the authoritative record of the ideas. This very dedication, however, has tended to mask his individual stature and there are some who regret the absence of the inspiration and innocence of his earlier writings which in his later year were only evident to those few individuals with whom he could relax. The author of the present book, who is himself an adept of many years standing, has endeavoured to portray the real nature of the man, who was not the austere intellectual of the classroom but a warm-hearted and rather lonely visionary to whom the world owes a great debt of gratitude, a debt which the author suggests can now in part be repaid by the acknowledgement of his genius. The sketch on the jacket by J. Waterhouse is based on a little-known photograph showing Ouspensky in the happy mood of his more relaxed moments - the 'Peter' aspect of his character as opposed to the more generally depicted austere, highly intellectual 'Darnian' guise.