CathInfo.com

I'm just curious if you or anyone else here can cite where the Angelic Doctor might have written this, or at least some other theologian.

"Some have asserted that witchcraft is nothing in the world but an imagining of men who ascribed to spells those natural effects the causes of which are hidden. But this is contrary to the authority of holy men who state that the demons have power over men's bodies and imaginations, when God allows them: wherefore by their means wizards can work certain signs. Now this opinion grows from the root of unbelief or incredulity, because they do not believe that demons exist save only in the imagination of the common people, who ascribe to the demon the terrors which a man conjures from his thoughts, and because, owing to a vivid imagination, certain shapes such as he has in his thoughts become apparent to the senses, and then he believes that he sees the demons. But such assertions are rejected by the true faith whereby we believe that angels fell from heaven, and that the demons exist, and that by reason of their subtle nature they are able to do many things which we cannot; and those who induce them to do such things are called wizards.