These past few chapters, including this one in particular, are the start of all science.
1 It is evident, next, that God is the cause enabling all operating agents to operate. In fact, every operating agent is a cause of being in some way, either of substantial or of accidental being. Now, nothing is a cause of being unless by virtue of its acting through the power of God, as we showed. Therefore, every operating agent acts through God’s power.
2 Again, every operation that results from a certain power is attributed causally to the thing which has given the power. For instance, the natural motion of heavy and light things results from their form, depending on whether they are heavy or light, and so the cause of their motion is said to be the generating agent that has given them the form. Now, every power in any agent is from God, as from a first principle of all perfection. Therefore, since every operation results from a power, the cause of every operation must be God.
Notes The cause of every operation at its base, at its first movement or change, he means.
3 Besides, it is obvious that every action which cannot continue after the influence of a certain agent has ceased results from that agent. For instance, the manifestation of colors could not continue if the sun’s action of illuminating the air were to cease, so there is no doubt that the sun is the cause of the manifestation of colors.
And the same thing appears in connection with violent motion, for it stops with the cessation of violence on the part of the impelling agent. But just as God has not only given being to things when they first began to exist, and also causes being in them as long as they exist, conserving things in being, as we have shown, so also has He not merely granted operative powers to them when they were originally created, but He always causes these powers in things. Hence, if this divine influence were to cease, every operation would cease. Therefore, every operation of a thing is traced back to Him as to its cause.
Notes This doesn’t account for inertia, obviously, but you get the idea.
4 Moreover, whatever agent applies active power to the doing of something, it is said to be the cause of that action. Thus, an artisan who applies the power of a natural thing to some action is said to be the cause of the action; for instance, a cook of the cooking which is done by means of fire. But every application of power to operation is originally and primarily made by God. For operative powers are applied to their proper operations by some movement of body or of soul.
Now, the first principle of both types of movement is God. Indeed, He is the first mover and is altogether incapable of being moved, as we shown above. Similarly, also, every movement of a will whereby Powers are applied to operation is reduced to God, as a first object of appetite and a first agent of willing. Therefore; every operation should be attributed to God, as to a first and principal agent.
5 Furthermore, in all agent causes arranged in an orderly way the subsequent causes must act through the power of the first cause. For instance, in the natural order of things, lower bodies act through the power of the celestial bodies; and, again, in the order of voluntary things, all lower artisans work in accord with the direction of the top craftsman.
Now, in the order of agent causes, God the first cause, as we showed in Book One . And so, all lower agent causes act through His power. But the cause of an action is the one by whose power the action is done rather than the one who acts: the principal agent, for instance, rather than the instrument. Therefore, God is more especially the cause of every action than are the secondary agent causes.
Notes This argument may strike moderns as “unfair”, especially in its first part. Which shows how far we have fallen.
6 Again, every agent is ordered through his operation to an ultimate end, for either the operation itself is the end, or the thing that is made, that is, the product of the operation. Now, to order things to their end is the prerogative of God Himself, as we showed above. So, we have to say that every agent acts by the divine power. Therefore, He is the One Who is the cause of action for all things.
7 Hence it is said: “Lord, Thou hast wrought all our works in us” (Is. 26:12); and: “Without Me, you can do nothing” (John 15:5); and: “It is God Who works in us both to will and to accomplish according to His good will” (Phil. 2: 13). And for this reason, the products of nature are often attributed, in Scripture, to divine working, because it is He Who works in every agent operating naturally or voluntarily, as the text has it: “Have you not milked me as milk, and curdled me like cheese? You have clothed me with skin; You have put me together with bones and sinews” (Job 10:10-11); and in the Psalm (17:14): “The Lord thundered from heaven, and the Highest gave His voice: hail and coals of fire.”