From An excerpt from the beginning:
Part I. - Incubation in Pagan Temples. - I. Introduction In the ancient science of divination, four working methods were commonly practised. Revelations of the future were deduced from natural portents, from the flight of birds, from entrails of sacrificial victims, or from dreams. It was the fourth way that had, for obvious reasons, the greatest vogue. Belief in the significance of dreams has always been widespread, and the supernatural authority attached to them by the ancients needs no demonstration. From Pharaoh's dream downwards there are recorded many illustrations of the importance with which they were regarded not only by the ignorant and superstitious, but by philosophical thinkers. The philosophy of dreams, as they were regarded in the fourth century B.C., was held to be that in sleep the soul was freed from the body so that it could soar into spiritual regions, and commune with divine beings. Accordingly, memories of what had passed in sleep were to be cherished as divine revelations granted to the soul. The science of oneiromancy was the subject of much study. Artemidoros of Ephesus has five books of Oneirocritica, where he attempts some explications and relates many instances of dreams. Dreams are divided by him into five classes, of which the fifth is the most important for divination.