Summa contra Gentiles3.100 Chapter C. That what God does beside the order of nature is not contrary to nature

It would seem, however, necessary to observe that although God sometimes does something beside the order assigned to things, he does nothing contrary to nature.

For since God is pure act, whereas all other things have some admixture of potentiality, it follows that God must be compared to all things as the mover to the thing moved, and as the active to the potential. Now, when that which in the natural order is in potentiality with regard to a certain agent, is acted upon by that agent, this is not contrary to nature simply, although sometimes it is contrary to that particular form which is corrupted by such action: thus when fire is generated, and air is corrupted through the action of the fire, both generation and corruption are natural. Consequently whatever is done by God in created things is not contrary to nature, although it may seem to be contrary to the order proper to a particular nature.

Again. Since God is the first agent, as we have proved, all subsequent agents are likened to His instruments. Now, the purpose of an instrument is to serve the action of the principal agent while it is being moved by it: wherefore the matter and form of an instrument must be such as to be suitable for the action intended by the principal agent, Hence it is not contrary but most becoming to the nature of an instrument to be moved by the principal agent. Neither, therefore, is it contrary to nature, that creatures be moved by God in any way whatsoever: since they were made that they might serve Him.

Further. Even in corporeal agents we observe that the movements resulting in inferior bodies from the influence of higher bodies, are neither violent nor unnatural, although they may seem unbecoming to the natural movement which the inferior body has, as being proper to its form: for we do not say that the ebb and flow of the sea is a violent movement, since it results from the influence of a heavenly body, although the natural movement of water is only in one direction, namely to the centre. Much less, therefore, can whatsoever God does in any creature, be described as violent or unnatural.

Besides. The first measure of every essence and nature is God, as the first being, which is the cause of being in all other things. Since then we judge of everything by its measure, we must regard as natural to a thing, that whereby it is conformed to its measure. Hence whatever is implanted in a thing by God, is natural to that thing. Therefore if something else be implanted by God in that same thing, it will not be unnatural.

Moreover. All creatures are compared to God, as works of art are compared to the artist, as appears from what we have already said. Hence all nature is the work of the divine art. Now it is not inconsistent with a work of art that the artist make some alteration in his work, even after giving it its first form. Neither, therefore is it contrary to nature if God does something in natural things, other than that which occurs in the ordinary course of nature. Wherefore Augustine says: God the creator and author of all natures, does nothing unnatural: because to each thing, that is natural which is caused by Him from whom is all measure, number and order in nature.