(CG 3/101). Of Miracles (Book 3. God, the End of Creatures) (Summa Contra Gentiles) (Aquinas, Thomas, St.)

WHAT is entirely subject to established order cannot work beyond that order. But every creature is subject to the order which God has established in nature. No creature therefore can work beyond this order, which working beyond the order of nature is the meaning of working miracles.

2. When any finite power works the proper effect to which it is determined, that is no miracle, though it may surprise one who does not understand the operation. But the power of every creature is limited to some definite effect, or effects. Whatever therefore is done by the power of any creature cannot properly be called a miracle. But what is done by the power of God, infinite and incomprehensible, is properly a miracle.

3. Every creature in its action requires some subject to act upon: for it belongs to God alone to make a thing out of nothing (B. II, Chap. XXI). But nothing that requires a subject for its action can act except to the production of those effects to which that subject is in potentiality: for the work of action upon a subject is to educe that subject from potentiality to actuality. As then a creature can never create, so it can never act upon a thing except to the production of that which is in the potentiality of that thing. But in many miracles done by divine power a thing is done, which is not in the potentiality of that upon which it is done, as in the raising of the dead.

Hence it is said of God: Who does great wonderful works alone(Ps. cxxxv, 4).