(CG 2/22). That God is Almighty (Book 2: God The Origin of Creatures) (Summa Contra Gentiles) (Aquinas, Thomas, St.)

The power of every necessary agent is determined and limited to one effect. That is the reason why all physical effects always come out in the same way, unless there be some interference: but acts of the will not so. But the divine power is not directed to one effect only (Chap. XXII). God then does not act by physical necessity, but by will.

2. Whatever does not involve a contradiction, is within the range of the divine power. But many things that do not exist in creation would still involve no contradiction if they did exist. This is most evidently the case in regard of the number and size and distances of the stars and other bodies. They would present no contradiction, no intrinsic absurdity, if they were arranged on another plan. Many things therefore lie within the range of divine power, that are not found in nature. But whoever does some and leaves out others of the things that he can do, acts by choice of will and not by physical necessity.

4. Since God's action is His substance (B. I, Chap. LXXIII), the divine action cannot come under the category of those acts that are 'transient' and not in the agent, but must be an act 'immanent' in the agent, such as are acts of knowing and desiring, and none other. God therefore acts and operates by knowing and willing.

6. A self-determined agent is prior to an agent determined from without: for all that is determined from without is reducible to what is self-determined, or we should have process to infinity. But he who is not master of his own action is not self-determined: for he acts as led by another, not as his own leader. The prime agent then must act in such a way as to remain master of his own action. But no one is master of his own action except he be a voluntary agent.

7. Will-action is naturally prior to physical action: for that is naturally prior which is more perfect, albeit in the individual it be posterior in time. But will-action is the more perfect, as within our experience voluntary agents are more perfect than physical. Therefore will-action must be assigned to God, the prime agent.

8. Where will-action and physical action go together, will-action represents the higher power and uses the other as an instrument. But the divine power is supreme, and therefore must act by will-action, not under physical necessity.

This truth also divine Scripture teaches us. All things, whatsoever he haswilled, the Lord hasdone (Ps. cxxxiv, 6): Who worketh all things according to the counsel of his will (Eph. i, 11).