Whence the performances of Magicians derive their Efficacy*

MAGICIANS in their performances use certain words with a meaning to the production of definite effects. Now a word, as meaning something, has no power except from some understanding, the understanding either of him who utters the word or of him to whom it is uttered: from the understanding of the utterer, in the case where a word is of such power that by the idea which it contains it is apt to produce real effects, the idea being applied to the production of those effects by the ministry of the voice: from the understanding of the person addressed, in the case when the hearer is induced to do something by the reception into his understanding of the idea conveyed by the word. Now it cannot be said that those words, uttered by magicians with a meaning, have their efficacy from the understanding of him who utters them. For, since power follows upon essence, difference of power argues a difference of essential principle. But we find the condition of the understanding of men generally to be such that it is more true to say that its cognition is caused by things than that any idea which it conceives can be the cause of things. If then there are any men who by words expressive of the concept of their understanding can change things one into another, and do that by power of their own (res possint transmutare propria virtute), they must be beings of another species from ordinary mortals, and cannot be called men in the sense in which others are men (dicentur aequivoce homines).* The alternative is to suppose that such effects are accomplished by the understanding of some person, to whom the speech of him who utters such words is addressed. This supposition has its confirmation in the fact that the expressions which magicians use consist of invocations, entreaties, adjurations, or even commands, as of one person talking with another.

Besides, in the ceremonies of this art they employ certain characters and geometrical figures. But a figure is no principle of action, imparted or received: or else mathematical drawings would be active and passive. Matter therefore cannot be disposed by geometrical figures to the reception of any natural effect. It follows that these figures are not used as disposing causes, but as signs. Now we use signs only to address other intelligent beings. Magical arts therefore owe their efficacy to some intelligence, to whom the speech of the magician is addressed, -- as is also shown by the sacrifices, prostrations, and other rites employed, which can be nothing else but signs of reverence paid to some intelligent nature.

3.104 : That the Works of Magicians are not due solely to the Influence of the Heavenly Spheres
3.106 : That the Subsistent Intelligence, which lends Efficacy to Magical Performances, is not Good in both Categories of Being