But if any one says that, once God has fixed an orderly course of events, He cannot change it without changing Himself; and that He would change Himself, if ever He worked in the world to the production of effects apart from their own proper causes, such a saying may be refuted by a study of nature. For the orderly course of events fixed by God, if we look at it as it obtains in creation, will be found to hold for the most part, but not everywhere or always:* for sometimes, although in a minority of cases, the thing turns out otherwise, either for lack of power in the agent, or for indisposition of the matter, or from some vis major supervening. Yet not on that account does the law of providence * fail or suffer change: for it comes under providence that the natural course of things, instituted to hold usually,* should sometimes fail. If therefore by the action of some created power the natural course of events may be altered from the usual to the unusual, and that without any alteration of divine providence, much more may the divine power sometimes do a thing, without prejudice to its own providence, beyond the course assigned to natural events by God. This God does at times to manifest His power: for there is no better way of manifesting the subjection of all nature to the divine will than by something being done at times beyond the course of nature: for thereby it appears that the course of events proceeds from Him, and is not of necessity of nature, but through free will.* Nor should this be accounted a frivolous reason to allege, that God works some effects in nature to the end of manifesting Himself to human minds, since it has been shown that all the material creation is subordinated to serve the end of intellectual nature, while the end of intellectual nature itself is the knowledge of God. No wonder then if some change is wrought in corporeal substance to afford intelligent nature a knowledge of God.
3.97 : How the Arrangements of Divine Providence follow a Plan
3.100 : That the things which God does beyond the Order of Nature are not contrary to Nature