Thomas Aquinas commenting on Ibn Sina's treatise on Evil Eye: Avicenna attributes the phenomenon of bewitchment (fascinationis) to the fact that matter innately obeys non-material beings rather than opposing natural agents. So when the soul’s imaginative power is strong, matter >

>is changed by it. This, he says, is the cause of the “evil eye” (oculis fascinantis). But it has been shown above that matter does not obey non-material beings at will, but
rather the Creator alone. Thus it is preferable to say that the spirits joined with the body are changed >

> by the imagination’s power. This change occurs mainly in the eyes, which the more subtle spirits reach. Now the eyes infect the air to a certain definite distance, just as new and untarnished mirrors become tarnished from the glance of a menstruating woman, as Aristotle says. >

> Thus, when certain souls are strongly stirred by wickedness, as happens especially with old women, their looks become spiteful and poisonous, particularly to children with tender and impressionable bodies. It is also possible that by God’s permission, or by virtue of some >

> hidden arrangement, the spitefulness of the demons (with whom the witches have some sort of compact) also plays a part in this. Aquinas, Summa Theologiae, 15:141.