1. If no inferior cause, and especially no corporeal cause, does any work, but God works alone in all agencies, and God does not change by working in different agencies; no difference of effect will follow from the difference of agencies in which God works: but that is false by the testimony of sense.
2. It is contrary to the notion of wisdom for anything to be to no purpose in the works of the wise. But if created things in no way work to the production of effects, but God alone works all effects immediately, to no purpose are other things employed by Him.
3. To grant the main thing is to grant the accessories. But actually to do follows upon actually to be: thus God is at once pure actuality and the first cause. If then God has communicated to other beings His likeness in respect of being, it follows that He has communicated to them His likeness in respect of action.
4. To detract from the perfection of creatures is to detract from the perfection of the divine power. But if no creature has any action in the production of any effect, much is detracted from the perfection of the creature: for it marks abundance of perfection to be able to communicate to another the perfection which one has oneself.
5. God is the sovereign good (B. I, Chap. XLI). Therefore it belongs to Him to do the best. But it is better for good conferred on one to be common to many than for it to be confined to that one: for common good always proves to be more godlike than the good of the individual. But the good of one comes to be common to many when it is derived from one to many, which cannot be except in so far as the agent diffuses it to others by a proper action of its own. God then has communicated His goodness in such a way that one creature can transmit to others the good which it has received.
6. To take away order from creation is to take away the best thing that there is in creation: for while individual things in themselves are good, the conjunction of them all is best by reason of the order in the universe: for the whole is ever better than the parts and is the end of the parts. But if actions are denied to things, the order of things to one another is taken away: for things differing in their natures are not tied up in the unity of one system otherwise than by this, that some act and some are acted upon.
7. If effects are not produced by the action of creatures, but only by the action of God, it is impossible for the power of any creature to be manifested by its effect: for an effect shows the power of the cause only by reason of the action, which proceeds from the power and is terminated to the effect. But the nature of a cause is not known through its effect except in so far as through its effect its power is known which follows upon its nature.* If then created things have no actions of their own productive of effects, it follows that the nature of a created thing can never be known by its effect; and thus there is withdrawn from us all investigation of natural science, in which demonstrations are given principally through the effect.*
Some Doctors of the Moorish Law are said to bring an argument to show that accidents are not traceable to the action of bodies, the ground of the argument being this, that an accident does not pass from subject to subject: hence they count it an impossibility for heat to pass from a hot body to another body heated by it, but they say that all such accidents are created by God. Now this is a ridiculous proof to assign of a body not acting, to point to the fact that no accident passes from subject to subject. When it is said that one hot body heats another, it is not meant that numerically the same heat, which is in the heating body, passes to the body heated; but that by virtue of the heat, which is in the heating body, numerically another heat comes to be in the heated body actually, which was in it before potentially. For a natural agent does not transfer its own form to another subject, but reduces the subject upon which it acts from potentiality to actuality.*
3.68 : That God is everywhere and in all things
3.70 : How the Same Effect is from God and from a Natural Agent