Imagination is actually as the eye of the soul, and it is therein that forms are delineated and preserved; by its means we behold the reflections of the indivisible world; it is the mirror of visions and the apparatus of magical life. Thereby we cure diseases, modify the seasons, ward off death from the living and resuscitate those who are dead, because this faculty exalts the will and gives it power over the universal agent.
Imagination is the instrument of the adaptation of the Logos. In its application to reason it is genius, for reason, like genius, is one amidst the complexity of operations. Demons, souls, and the rest, can therefore by really and truly beheld by means of the imagination; but the imagination of the adept is diaphonous, whilst that of the uninitiated is opaque. The light of truth traverses the one as through a crystal window, and is refracted in the other as in a vitreous mass full of scoriae and foreign matter.
The things which contribute most to the errors of the vulgar and the extravagances of the insane are the reflection of depraved imaginations in one another. But the seer knows with an absolute knowledge that the things he imagines are true and experience invariably confirms his visions.
Eliphas Levi, The Mysteries of Magic