Oneiromancy is the interpretation of dreams as omens or messages that reveal the future or disclose hidden truths, resting on the ancient and widespread belief that dreams carry meaning, from a god, the spirits, the dead, or the deeper self, encoded in symbols that a skilled interpreter can unlock. It is among the oldest of the divinatory arts.
Mesopotamian scribes compiled dream-omen manuals (the Assyrian "Dream Book"); the Egyptians kept dream-keys; the Hebrew Bible gives dream-interpretation a starring role in the stories of Joseph, who reads Pharaoh's dreams of the fat and lean cattle, and Daniel at the Babylonian court; and Greek and Roman antiquity produced the most famous of all dream-manuals, the Oneirocritica of Artemidorus of Daldis, a systematic second-century guide to the meaning of dream-symbols that already distinguished predictive dreams from those merely reflecting the dreamer's state.
Temples of the healing god Asclepius practised dream-incubation, in which the sick slept in the sanctuary to receive a curative or diagnostic dream. This tradition of reading dreams as objective messages was profoundly reoriented in the modern era by psychology: Freud's Interpretation of Dreams recast the dream not as a message about the outer future but as a disguised expression of the dreamer's own unconscious wishes, and Jung read dream-symbols as communications from deeper layers of the psyche. Oneiromancy thus stands at the crossroads of divination and psychology, the age-old conviction that dreams mean something, interpreted first as prophecy and later as a window on the self.