This was Plato's theory. He felt that there was another world that was unchanging and perfect, while ours is temporal and constantly changing. He believed the other world was more real, as it did not change. His teachings heavily influenced Christian teaching on heaven. (For those who object to this, C.S. Lewis recognized this. At the end of Chronicles of Narnia the character based on himself says something like "Its all in Plato. What are they teaching these days in the schools?")I prefer Aristotle, who was concerned with this world and what we can actually know.

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