Thomas Aquinas, Compendium of Theology

We can see from the foregoing that all things are governed by divine providence. Whatever is set in motion toward the end intended by any agent, is directed by that agent to the end. Thus all the soldiers in an army are subordinated to the end intended by the commander, which is victory, and are directed by him to that end. We showed above that all things tend by their actions to the divine goodness as their end. Hence all things are directed to this end by God Himself, to whom this end pertains. To be thus directed is the same as to be ruled and governed by providence. Therefore all things are ruled by divine providence.

Moreover, things that are subject to failure and that do not always remain constant, are found to be under the direction of beings that do remain constant. Thus all the movements of lower bodies, being defectible, are regulated in accordance with the undeviating movement of a heavenly body. But all creatures are changeable and defectible. As regards intellectual creatures, their very nature is such that deficiency in voluntary action can develop in them. Other creatures have some part in movement, either by way of generation and corruption, or at least according to place. God Himself is the only being in whom no defect can arise. Consequently all creatures are kept in order by Him.

Furthermore, whatever has existence by way of participation, is traced back, as to its cause, to that which exists in virtue of its own essence; for example, what is on fire has, in some way or other, fire as the cause that ignited it. Since God alone is good by His very essence, and all other things receive their complement of goodness by some sort of participation, all beings must be brought to their complement of goodness by God. This, again, involves rule and government; for things are governed or ruled by being established in the order of good. And so all things are governed and ruled by God.