In Thomas Aquinas’ work titled On Truth (De Veritate), Thomas deals with whether or not the world is ruled by God’s providence, or whether all natural things happen randomly. Thomas even precedes his comments by positing a potential objector who says that if God were providentially moving all nature, we ought to be able to observe nature and determine God’s purposes, but we cannot do such a thing. Thomas gives us a most interesting comment in his response:
Whatever does not have a determinate cause happens by accident. Consequently, if the position mentioned above were true, all the harmony and usefulness found in things would be the result of chance. This was actually what Empedocles held. He asserted that it was by accident that the parts of animals came together in this way through friendship—and this was his explanation of an animal and of a frequent occurrence! This explanation, of course, is absurd, for those things that happen by chance, happen only rarely; we know from experience, however, that harmony and usefulness are found in nature either at all times or at least for the most part. This cannot be the result of mere chance; it must be because an end is intended. What lacks intellect or knowledge, however, cannot tend directly toward an end. It can do this only if someone else’s knowledge has established an end for it, and directs it to that end. Consequently, since natural things have no knowledge, there must be some previously existing intelligence directing them to an end, like an archer who gives a definite motion to an arrow so that it will wing its way to a determined end. Now, the hit made by the arrow is said to be the work not of the arrow alone but also of the person who shot it. Similarly, philosophers call every work of nature the work of intelligence. (DV, Q5, A2)
So Thomas considers the idea that the effects of the natural world happen by accident, even to the point of considering that parts of animals could come together due to their contact with each other, and considers this explanation absurd. His reason is that things that happen by chance, at least the useful things, happen only rarely, yet everything we observe in nature happens regularly. Harmony and usefulness are found always or at least usually, and this does not align with things happening by chance. That nature moves toward an end is evidence that an end is intended, and anything that lacks knowledge and happens randomly is not directed toward an end. Since natural things have no knowledge, there must be an external intellige3nce directing them toward an end.
Modern atheist evolutionists tell us that nature is completely purposeless, yet works toward an end, namely survival. For the most part this end is assumed and never questioned, and we are told that all of nature is mindless and random, yet driven toward an end. Thomas Aquinas thought of this position 750 years ago and called it absurd.
As for why nature and creatures do not work perfectly nor are perfectly aligned toward their ends, Thomas thought of this also. Creatures are flawed, and have weakness of body and of intellect, and therefore do not reflect their Creator’s designed ends perfectly. (see Difficulty & Answer 11) So the flaws we find in nature are not the fault of the Creator, but of the sin which entered the world and marred the creation. Our inability to observe nature and determine God’s purposes are due to our feeble intelligence, not the lack of God’s providence.
Aquinas’ explanation of divine providence is much more plausible than what we are commonly told today, which is that mindless random accident creates order, and that nature does not work toward an end, except in the case of the end of survival, which we are told to assume rather than question why this is so.