"Tertium Organum: A Key to the Enigmas of the World" by P.D. Ouspensky is a philosophy book published in 1947 by Knopf. It delves into the mysteries of the world and offers a unique perspective on philosophical concepts. The book, originating from the United States of America, challenges readers to question and explore the deeper aspects of reality and existence. With its thought-provoking ideas, "Tertium Organum" is a collectible item for those interested in philosophy and the enigmas of the world.