The waking have one world in common; sleepers have each a private world of his own.
τοῖς ἐγρηγορόσιν ἕνα καὶ κοινὸν κόσμον εἶναι, τῶν δὲ κοιμωμένων ἕκαστον εἰς ἴδιον ἀποστρέφεσθαι
Original text (Ancient Greek)
Notes from Wikiquote
Plutarch, Of Superstition