Question Three of Chapter Eight of the Third Decade
Whether fascination is a natural or diabolical work
It is asked whether the fascination of infants and boys by old sorceresses is a natural or diabolical work.
To this it is answered thus. Avicenna held that the cause of fascination was perhaps the powerful imagination of the soul.
For just as someone walking upon a beam placed high up falls easily because through fear he imagines a fall; and just as, merely at the soul’s apprehension, the body grows warm, as is evident in the lustful and the angry, or is chilled, as in the fearful; and just as the body is sometimes also altered by a powerful apprehension into some sickness, such as fever or leprosy; so too the soul of an old woman, vehemently affected toward malevolence, impresses harm upon someone, especially upon a boy who, because of the tenderness of his body, is most susceptible to impressions.
According to Avicenna, it follows from this that corporeal matter would obey a spiritual substance at will.
But since it was said above that corporeal matter obeys a spiritual substance only with respect to local motion, and obeys God alone at will, it is therefore better to say that the fascination of boys arises from the powerful imagination of the old woman’s soul altering the spirits of the conjoined body. This alteration of the spirits occurs especially in the eyes, to which the more subtle spirits come.
The eyes then infect the continuous air as far as a determinate space. In this manner, if mirrors are new and clean, they contract a certain impurity from the gaze of a menstruating woman, as Aristotle says in the book On Sleep and Waking.
Thus, when the soul of an old woman has been moved vehemently toward malevolence, her gaze is made poisonous and harmful in the manner just described, especially to boys, who possess a tender body and easily receive an impression.
It is also possible that, with God permitting it, the malice of demons cooperates in this, since old sorceresses have some covenant with them.
These things are from Thomas, Book II of the Summa contra Gentiles, chapter 103, and the First Part, question 117, article 3, reply to the second argument.