Summa contra Gentiles3.103 Chapter CIII. That spiritual substances do wonders which, how- ever, are not miracles properly speaking

It was the opinion of Avicenna that matter is more obedient to separate substances in the production of an effect, than to contrary agents in matter. Hence he states that sometimes, at the apprehension of the aforesaid substances, an effect ensues in this lower world, such as rain, or the health of a sick person, without any corporeal agent intervening.

He regards as a sign of this the fact that when our soul is of strong imagination, the body is affected by mere thought: thus a man while walking on a plank at a height, easily falls, because through fear he imagines himself to fall: whereas he would not fall, were the plank placed on the ground, so that he would not fear to fall. It is also clear that the body is heated at a mere apprehension of the soul, for instance in lustful or angry persons; or again, becomes cold, as happens in those who are seized with fear. Sometimes too, through a strong apprehension, it is inclined to some illness, for instance fever or even leprosy. In this way, says he, if the soul be pure and not subject to the passions of the body, and strong of apprehension, not only its own body is obedient to its apprehension, but even external bodies: so much so that a sick man be healed or something similar occur, at its mere apprehension. He holds this to be the cause of fascination: because, to wit, a certain person’s soul being deeply affected with malevolence, exercises a baneful influence on someone, especially on a child, who by reason of the softness of the body is most impressionable. Hence he maintains that much more, without the action of a corporeal agent, do certain effects result in these lower bodies, at the apprehension of separate substances, which, he says, are the souls or movers of the spheres.

This theory is consistent enough with other opinions of his. For he holds that all substantial forms emanate from a separate substance into these lower bodies; and that corporeal agents merely dispose matter to receive the impression of the separate agent. But this is untrue according to the teaching of Aristotle, who proves (7 Metaph.), that the forms which are in matter, do not come from separate forms, but from forms in matter: for thus it is that we find a likeness between the maker and the thing made.

Moreover, the comparison with the soul’s impression on the body does not advance his theory very much. For no impression is made on the body as a result of an apprehension, unless united to the apprehension there be some emotion, as of joy, fear, desire, or of some other passion. Now these passions are accompanied by a certain definite movement of the heart, the result being an impression on the entire body, either as to local motion, or as to some alteration. Hence it still remains that the apprehension of a spiritual substance does not make an impression on the body, except by means of local movement.

As to his remark about fascination, this is not due to the apprehension of one affecting immediately the body of another: but it results from that apprehension affecting the conjoined body through the movement of the heart, the influence of which reaches even to the eye, which is able to work evil on an external object, especially if it be easily impressionable: thus the eye of a woman in her menses infects a mirror.

Accordingly, except through the local movement of a body, a created spiritual substance cannot, by its own power, induce any form into corporeal matter, as though matter were in this obedient thereto, so as to become actuated by a certain form. For it is in the power of a created spiritual substance, that a body should be obedient to it in respect of Iii. ii local movement. And by moving a particular body locally, it applies certain natural forces to the production of certain effects: thus the art of the smith applies fire to make the iron malleable. But this is not miraculous, properly speaking. It follows, therefore, that created spiritual substances do not work miracles by their own power. And I say by their own power: because nothing prevents these substances from working miracles, in so far as they work by divine power. This indeed may be seen from the fact that as Gregory states one order of angels is especially deputed to the working of miracles. He also says that certain saints sometimes work miracles by power, and not merely by intercession.

We must observe, however, that when angels or demons apply natural things in order to produce certain definite effects, they employ them as instruments, just as a physician uses certain herbs as instruments for the purpose of healing. Now, from an instrument there proceeds an effect, not only in proportion to its power, but also in excess thereof, forasmuch as it acts by the power of the principal agent: thus a saw or an axe could not produce a bedstead except through being applied by craftsmanship for that particular effect: nor could natural heat produce flesh, except by the power of the vegetative soul, that employs it as an instrument. It is therefore reasonable that certain higher effects should result from these same natural things, through spiritual substances employing them as instruments.

Accordingly, although such effects cannot be called miracles absolutely, since they result from natural causes, yet are they wonderful to us in two ways. First, because these causes are applied for the production of their proper effects by spiritual substances in a way that is strange to us: even so the works of skilful craftsmen seem wonderful to others who see not how the work is done.-—Secondly, because the natural causes employed for the production of certain effects are invested with a certain power through serving as instruments of spiritual substances: and this comes nearer to the nature of a miracle.