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 two phrases come from the Diels-Kranz fragment B89 of Heraclitus: ὁ Ἡράκλειτός φησι τοῖς ἐγρηγορόσιν ἕνα καὶ κοινὸν κόσμον εἶναι τῶν δὲ κοιμωμένων ἕκαστον εἰς ἴδιον ἀποστρέφεσθαι («Heraclitus said that the waking have one common world, but the sleeping turn aside each into a world of his own.»)
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.