That there is such a thing is certain, even from Cicero as witness, whose two books on it survive. It seems to be nothing other than the signification of hidden things from covenants agreed with a demon. I say signification, because it is not completed by the intellective or cognitive act of the mind alone, but also uses outward signs and words; in this respect it differs from the judgment acquired through vain observance. It concerns past and present things as well as future things, provided that those things are hidden, that is, far removed from human cognition. Therefore I have preferred to say “of hidden things” rather than “of future things.” For prophecy and divination agree in their matter.
The things added about a covenant with a demon separate divination from prophecy and from natural conjectation. The latter is born from discipline and human observation; the former, however, is infused from above by God. Since all divination, whatever it is, depends upon the help of a demon, who imitates divinity by stealing divination, whence it is also called divination as if an imitation of divinity, it follows that divination cannot advance further than the demon’s knowledge extends. It also follows that divination is not performed by art or by nature.
Magi use various instruments for it. One who has an express pact with a demon, knowing that nothing happens more pleasingly to him than the idolatrous worship of human beings, generally interposes sacrifice, after an altar has been set up, prayers recited, incense lit, and garments worn like those of our priests. Yet they do not always do this, either because narrowness of time does not permit it, or because the form of divination which they are using does not require it. For there are several and diverse forms, as I shall teach later. Those who have a tacit pact use various observances according to the nature of the crime, not indeed sacrificing, but nevertheless referring the things they do and say, knowingly or unknowingly, to the honor of the demon.
[margin: Cicero, On Divination; Grillandus on pact with demons and divination]