Summa contra Gentiles3.105 Chapter CV. Whence the works of magicians derive their efficacy

It remains for us to inquire whence the magic arts derive their efficacy: a question that will present no difficulty if we consider their mode of operation.

For in the practice of their art they make use of certain 1 See end of ch. lxxxiv.

significative words in order to produce certain definite effects. Now, words, in so far as they signify something, have no power except as derived from some intellect; either of the speaker, or of the person to whom they are spoken. From the intellect of the speaker, as when an intellect is of such great power that it can cause things by its mere thought, the voice serving to convey, as it were, this thought to the things that are to be produced. From the intellect of the person to whom the words are addressed, as when the hearer is induced to do some particular thing, through his intellect receiving the signification of those words. Now, it cannot be said that these significative words uttered by magicians derive efficacy from the intellect of the speaker. For since power follows essence, diversity of power indicates diversity of essential principles. Moreover, man’s intellect is invariably of such a disposition that its knowledge is caused by things, rather than that it is able by its mere thought to cause things. Consequently if there be any men that are able of their own power to transform things by words expressive of their thoughts, they will belong to another species, and it would be an equivocation to call them men.

Further. By learning we acquire, not the power to do a thing, but the knowledge of how to do it. Yet some, by learning, are rendered able to perform these magic works. Therefore they must have not only knowledge but also the power to produce these effects.

If someone say that these men, by the influence of the stars, are born with the aforesaid power, while others are excluded from it; so that however much the others, who are born without this power, may be instructed, they cannot succeed in performing these works; we reply, first that, as shown above, heavenly bodies cannot make an impression on the intellect. Therefore a man’s intellect cannot, through the influence of the stars, receive a power whereby the vocal expression of its thoughts is productive of something.

And if it be said that the imagination produces an effect in the utterance of significative words, and that heavenly-bodies can work on the imagination, since its operation is performed by a bodily organ:—this does not apply to all the results produced by this art. For we have shown that these effects cannot all be produced by the power of the stars. Neither, therefore, can anyone by the power of the stars, receive the power to produce those effects. Consequently it follows that these effects are accomplished by an intellect to whom the discourse of the person uttering these words is addressed. We have an indication of this in the fact that the significative words employed by the magician are invocations, supplications, adjurations, or even commands as though he were addressing another.

Again. Certain characters and definite figures are employed in the observances of this art. Now a figure cannot be the principle of either action or passion; else, mathematical bodies would be active and passive. Therefore matter cannot, by definite figures, be disposed to receive a certain natural effect. Therefore magicians do not employ figures as dispositions. It remains, then, that they employ them only as signs, for there is no third solution. But we make signs only to other intelligent beings. Therefore the magic arts derive their efficacy from another intelligent being, to whom the magician’s words are addressed.

And if someone say that certain figures are appropriate to certain heavenly bodies; and so the lower bodies are determined by certain figures to receive the impressions of certain heavenly bodies:—seemingly this is an unreasonable statement. For the patient is not directed to receive the impression of the agent, except through being in potentiality. Hence those things alone determine it to receive a particular impression, that cause it to be somehow in potentiality. Now figures do not cause matter to be in potentiality to any particular form, because a figure, as such, abstracts from all matter and sensible forms, since it is something mathematical. Therefore a body is not determined by figures or characters to receive the influence of a heavenly body.

Besides. Certain figures are appropriate to heavenly bodies as the effects thereof; for the figures of the lower bodies are caused by heavenly bodies. Now, the aforesaid arts do not use characters or figures as produced by heavenly bodies, in fact they are produced by man in the practice of the art. Therefore the appropriateness of figures to certain heavenly bodies has nothing to do with the question.

Further. As we have shown, matter is nowise disposed to form by means of figures. Hence the bodies on which these figures are impressed, are as capable of receiving the influence of heavenly bodies, as other bodies of the same species. Now, that a thing act on one rather than another of several equally disposed, by reason of something appropriate to be found in it, is a mark of its operating not by natural necessity, but by choice. Hence it is clear that these arts which employ figures in order to produce certain effects, derive their efficacy, not from something that acts by nature, but from some intellectual substance that acts by intelligence. This is also proved by the very name of character which they apply to these figures: for a character is a sign. Whereby we are given to understand that they employ these figures merely as signs shown to some intellectual nature.

Since, however, in the products of art figures are like specific forms, someone might say that there is no reason why, through the influence of a heavenly body, some power should not shape the figure that gives an image its species, not indeed as a figure, but as specifying the product of art, which acquires this power from the stars. But as to the letters that form an inscription on an image, and other characters, nothing else can be said of them, but that they are signs: wherefore they are directed to an intelligence only.—This is also proved by the sacrifices, prostrations and other similar practices, which can be nothing else than signs of reverence shown to an intellectual nature.