An awareness that reality

embraces innumerable levels of existence was common to all the cultures of Antiquity and the Middle Ages, whether this was expressed in mythological or philosophical form. That the whole of reality should consist of the physical world which can be comprehended by our five senses is a very recent concept, and one which is basically contradicted by any knowledge of oneself. For man readily discovers that the stuff (so to speak) of which his soul is made is different from that of his body, and that for all its ties to the physical world, it possesses qualities that the body does not possess, such as perception, thought, and independent action. Endowed with these faculties, the soul is not, however, the only non-physical condition of human existence. For the soul, with its constant changes, is itself an object of knowledge, and this presupposes that there is something like an inner eye that sees the soul, while itself remaining constant. This is the Intellect in the medieval acceptance of this word. To try and comprehend it would be as hopeless as an attempt to see one's own faculty of vision. It transcends thought, yet it lends all possible certainty to thought. All rational evidence would be nothing without the truths that are a direct illumination from the Intellect. The medieval philosophers refer to the active intellect intellectus agens in Latin, al-′aql al′fâ′âl (in Arabic), because the Intellect consists, as it were, of the pure act of knowing, and never itself becomes the passive object of perception.

Titus Burckhardt, Moorish Culture in Spain