I answer that, 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.
Wherefore others have maintained that witchcraft can set up an impediment to carnal copulation, but that no such impediment is perpetual: hence it does not void the marriage contract, and they say that the laws asserting this have been revoked. But this is contrary to actual facts and to the new legislation which agrees with the old.
We must therefore draw a distinction: for the inability to copulate caused by witchcraft is either perpetual and then it voids marriage, or it is not perpetual and then it does not void marriage. And in order to put this to practical proof the Church has fixed the space of three years in the same way as we have stated with regard to frigidity (Article [1]). There is, however this difference between a spell and frigidity, that a person who is impotent through frigidity is equally impotent in relation to one as to another, and consequently when the marriage is dissolved, he is not permitted to marry another woman. whereas through witchcraft a man may be rendered impotent in relation to one woman and not to another, and consequently when the Church adjudges the marriage to be dissolved, each party is permitted to seek another partner in marriage.