Oneiromancy is the art of divining the future through our dreams. Nightmares were not used for this form of divination, as tradition dictated that these bad dreams were caused by demons.
Ancient Egyptians practiced dream divination. Each time the Pharaoh dreamed, a cast of priests devoted to the god Amun-Re would interpret the images, seeking clues to the future.
The Bible mentions oneiromancy several times, particularly in the Old Testament. In dreams, Solomon conversed with God and Joseph dreamed of success. In the Book of Daniel, Daniel was a dream interpreter.
Various philosophers through the ages have studied dreams. Ancient Greeks like Aristotle and PlatoRideout dreams. An ancient dream book, the Oneirocritica, was used by the ancient Greeks. Within this book is a list of ancient authors who studied dreams extensively. While the original works are lost, the Oneirocritica provides a valuable reference to information long thought lost.