Summa contra Gentiles2.23 Chapter XXIII. That God does not act of natural necessity

From this it may be proved that God acts among creatures not by necessity of His nature, but by the judgment of His will.

For the power of every agent that acts of natural necessity is confined to one effect. The consequence is that all natural things always happen in the same way, unless there be an obstacle; whereas voluntary things do not. Now the divine power is not directed to only one effect, as we have proved above. Therefore God acts, not of natural necessity, but by His will.

Again. Whatever implies no contradiction, is subject to the divine power, as we have proved. Now many things are not among those created, which nevertheless, if they were, would not imply a contradiction: as is evident chiefly with regard to number, the quantities and distances of the stars and other bodies, wherein if the order of things were different, no contradiction would be implied. Wherefore many things are subject to the divine power that are not found to exist actually. Now whoever does some of the things that he can do, and does not others, acts by choice of his will and not by necessity of his nature. Therefore God acts not of natural necessity but by His will.

Again. Every agent acts according as the likeness of its effect is in it: for every agent produces its like. Now whatever is in something else, is in it according to the mode of the thing in which it is. Since, then, God is intelligent by His essence, as we have proved, it follows that the likeness of His effect is in Him in an intelligible way. Therefore He acts by His intellect. Now the intellect does not produce an effect except by means of the will, the object whereof is a good understood, which moves the agent as his end. Therefore God works by His will, and not by a necessity of His nature.

Moreover. According to the Philosopher (9 Metaph.), action is twofold: one which remains in the agent and is its perfection, for instance to see; the other, which passes into outward things and is a perfection of the thing done, as to burn in the case of fire. Now God’s action cannot belong to the kind of actions which are not in the agent: since His action is His substance, as already proved. Therefore it must be of that kind of actions which are in the agent, and are as a perfection thereof. But the like are only the actions of one who has knowledge and appetite. Therefore God works by knowing and willing: and consequently not by a necessity of His nature, but by the judgment of His will.

Further. That God works for an end can be evident from the fact that the universe is not the result of chance, but is directed to a good, as stated by the Philosopher (ii Metaph.). Now the first agent for an end must be an agent by intellect and will: because things devoid of intellect, work for an end as directed to the end by another. This is evident in things done by art: for the flight of the arrow is directed towards a definite mark by the aim of the archer. And so likewise must it be in the works of nature. For in order that a thing be rightly directed to a due end, it is necessary that one know the end itself, and the means to that end, as also the due proportion between both; and this belongs only to an intelligent being. Since, therefore, God is the first agent. He works not by a necessity of His nature, but by His intellect and will.

Moreover. That which acts by itself precedes that which acts by another: because whatever is by another must be reduced to that which is by itself, lest we proceed to infinity- Now that which is not master of its own action, does not act by itself; since it acts as directed by another and not as directing itself. Therefore the first agent must act in such a way that it is master of its own action. But one is not master of one’s own action except by the will. Therefore it follows that God, Who is the first agent, acts by His will and not by a necessity of His nature.

Again. The first action belongs to the first agent, as the first movement to the first movable. Now, the action of the will naturally precedes the action of nature: because the more perfect is naturally first, although in some particular thing it may be last in time. Now the action of a voluntary agent is more perfect: a proof of which is that among us agents which act by will are more perfect than those which act by natural necessity. Therefore to God, Who is the first agent, that action is due which is by the will.

Further. The same is evident from the fact that where both actions are united, the power which acts by will is above that which acts by nature, and uses the latter as an instrument: for in man the intellect which acts by the will is higher than the vegetative soul which acts by a necessity of its nature. Now the divine power is above all beings. Therefore it acts on all things by will, not by natural necessity.

Again. The will has for its object a good considered as a good: whereas nature does not compass the idea of good in general, but the particular good which is its perfection. Since, then, every agent acts for as much as it intends a good, because the end moves the agent, it follows that the agent by will is compared to the agent by natural necessity as a universal to a particular agent. Now the particular agent is compared to the universal agent, as posterior thereto, and as its instrument. Therefore the first agent must be voluntary and not an agent by natural necessity.

Divine Scripture teaches us this truth. For it is said in the psalm Whatsoever the Lord pleased He hath done, and (Eph. i. ii): Who worketh all things according to the counsel of His will.

Hilary also in his book De Synodis says: God’s "will gave substance to all creatures. And further on: All things were created such as God willed them to be.

Hereby also is refuted the error of certain philosophers who asserted that God works by natural necessity.