Peter D. Ouspensky (March 4, 1878–October 2, 1947), (Pyotr Demianovich Ouspenskii, also Uspenskii or Uspensky, Пётр Демья́нович Успе́нский), a Russian esoteric philosopher known for his expositions of the early work of the Greek-Armenian teacher of esoteric doctrine George Gurdjieff, whom he met in Moscow in 1915. Ouspensky studied the Gurdjieff System directly under Gurdjieff's own supervision for a period of ten years, from 1915 to 1924. Ouspenky's book "In Search of the Miraculous" is a recounting of what Ouspensky learned from Gurdjieff during those years.
"No one can achieve illumination without having been previously purified. Only those that have achieved purification and sanctity can enter into the hall of illumination."