The ancient understanding of the universe was as a unified whole. Parmenides described the universe as a single, unified block of being. Then Plato split apart this unity with his ontological distinction between Heaven and Earth. Descartes’s mind-body dualism further removed humanity from nature by excluding consciousness from the natural world. Following Descartes, the major unresolved philosophical and scientific mystery has hinged on explaining the relationship between the fact of consciousness and the assumed insentience of nature.