P. D. Ouspensky
Pyotr Demyanovich Uspensky (Russian: Пётр Демьянович Успенский; 5 March 1878 – 2 October 1947), known in English as P. D. Ouspensky, was a Russian philosopher and esotericist known for his expositions of the early work of the Greek-Armenian teacher of esoteric doctrine George Gurdjieff. He met Gurdjieff in Moscow in 1915, and was associated with the ideas and practices originating with Gurdjieff from then on.