Idios kosmos comes from Greek and means private world. It exists with, and is opposite to, koinos kosmos (shared world). Idios kosmos is the view of the world that is developed from personal experience and knowledge and is therefore unique; however, it can be difficult to tell the difference between it and koinos kosmos. The idea of idios kosmos is an important part of Philip K. Dick's views on schizophrenia, as expressed in his 1964 essay "Schizophrenia & 'The Book of Changes'", drawing on personal experience with the I Ching.