Theurgia, or The Egyptian Mysteries (includes Letter to Anebo)

In the same way, many arrive at a perception of the future through an inspired rapture and a divine impulse, even while remaining fully awake with their senses in complete activity. Nevertheless, they do not follow the matter as closely as they would in their ordinary state of mind. Likewise, others among these ecstatics become divinely inspired when they hear cymbals, drums, or specific choral chants. Examples include those engaged in the Korybantic Rites, those possessed at the Sabazian festivals, and those celebrating the Rites of the Divine Mother. Others are inspired by drinking water, such as the priest of the Klarian Apollo at Kolophon; others by sitting over cavities in the earth, like the women who deliver oracles at Delphi; others by inhaling vapors from water, like the prophetesses at Branchidæ; and others by standing within marked-out spaces, having been filled by an imperceptible inflowing of the divine fullness (plerome).

Still others, while remaining self-aware in other respects, become inspired through their Imagination: some by using darkness, others by employing certain potions, and others by depending on chants and magical figures. Some are affected through water, others by gazing at a wall, others by the open air (hypethral), and others by the sun or other heavenly bodies. Some have also established the technique of seeking the future through entrails, birds, and stars.

I ask, what is the nature of divination, and what is its specific character? All diviners claim that they arrive at foreknowledge through gods or spirits (dæmons), and that it is impossible for others to have any inkling of these things—only those who have command over what is to come. I dispute, therefore, whether divine power is brought down to such a state of subservience to human beings that it would, for instance, not hold itself aloof from any person who acts as a diviner using only barley-meal.

Regarding the origins of the oracular art, it is doubtful whether a god, angel, spirit, or other such being is truly present at the Manifestations (original: "ἐπιφανεία" epiphany—an apparition or manifestation, such as was exhibited in mystic and theurgic rites.) or at the divinations, or any other Sacred Performances, merely because they were drawn there by the necessities created by your invocations.