Whether evolution via natural selection is a counter-example to Thomas's Fifth Way

Thomas Aquinas famously shows that the existence of God may be shown through five ways.  The fifth way is sometimes called the teleological argument or the argument from design.

The fifth way is taken from the governance of the world. We see that things which lack intelligence, such as natural bodies, act for an end, and this is evident from their acting always, or nearly always, in the same way, so as to obtain the best result. Hence it is plain that not fortuitously, but designedly, do they achieve their end. Now whatever lacks intelligence cannot move towards an end, unless it be directed by some being endowed with knowledge and intelligence; as the arrow is shot to its mark by the archer. Therefore some intelligent being exists by whom all natural things are directed to their end; and this being we call God.

Thomas begins with the rational principle that all things that act toward an end must have been designed to act toward this end.  Hence, if we find that there are ends, that agents act "as to obtain the best result", then we must agree that these agents' actions had a designer.  Thomas finds such agents in nature, agents that lack intelligence yet act in ways that are obviously "aimed" as, famously, "the arrow is shot to its mark by the archer".  Here Thomas is supposing these agents are programmed to act, they do not decide for themselves, e.g., birds fly south due to their DNA, not out of free choice.


Thomas focuses on nature and so his argument has lost some influence among modern man, who would more easily (and scientifically) attribute the ends of nature to natural selection and evolution.  To stay with the analogy, even a dumb archer will guide an arrow given enough time and motivation.  For example, Richard Dawkins argues that

Thanks to Darwin, it is no longer true to say that nothing we know looks designed unless it is designed.  Evolution by natural selection produces an excellent simulacrum of design, mounting prodigious heights of complexity and elegance.  And among these eminences of pseudo-design are nervous systems which -- among their more modest accomplishments -- manifest goal-seeking behavior that, even in a tiny insect, resembles a sophisticated heat-seeking missile more than a simple arrow on target (p. 103, God Delusion).

Evolution is undoubtedly true, and natural selection is the most likely scientific explanation for the way in which we ended up with complex organs like nervous systems.  But I doubt that evolution by natural selection is a valid counter-example to Thomas's fifth way.  Such arguments miss the deeper philosophical point contained within Thomas's argument.


Thomas remarks that at least some natural, unintelligent agents act to obtain the best result.  They do not end up acting at random (fortuitously), but in a way that best suits them.  It is the notion of best that implies a designer, even given evolution as the method of achieving that result.  For example, a dumb archer may eventually be trained to aim at a target, but it is a rational impossibility that a dumb archer chooses his target.  He shoots where he is told.  His notions of best are external, decided by a more able mind.  So if we wish to argue against Thomas's divinely driven nature, we cannot point toward evolution because it does not provide a definition of best.  It does not aim the arrow of nature, it merely propels it.  


To make this point clear, consider what one may say is the best human organ, the brain.  In his lecture notes on Aquinas, Peter Kreeft writes

I think Aquinas would say that evolution is an excellent example of cosmic design, evidence for God. He’d say the arrow of evolution flies to the target of human brains only because it’s guided by the intelligence of a divine archer. Aquinas would not be among the anti-Darwinian fundamentalists today. I think if he saw the atheist bumper sticker of the Christian fish with the word Darwin in it, he would not understand the intended irony, he would interpret it as an argument for theism (p. 20, The Philosophy of Thomas Aquinas). 

Using Dawkins's words, that there are bodily "eminences", we actually argue for God's existence. If we suppose that the action of our grey matter is the pinnacle of evolution, then we must concede to Aquinas that there is a designer, aiming the arrow of evolution toward human intelligence.  (God is the intelligence designer not the Intelligent Designer.)


A proper counter-example could be formed if it could be proven that there is no notion of best.  Instead, there are just flavors and variations, each equally valid.  So Thomas's archer may hit the bullseye, or he may avoid it, but we cannot rationally suppose one target is better than another.  This is a post-modern critique of Thomas.  But such an argument is not only fatal to Thomas's fifth way, but fatal to science as well.  Science needs best too, because it tells us truths about the physical world; it needs a best hypothesis.  Without best, the flat Earth and the round Earth become equals, and science would become a glorified database of physical occurrences.


This is why science is indebted to Aquinas and his fifth way.  He justifies the otherwise arrogant claim of scientific truth by telling us why we have intelligence: because our minds, made in the image of God's omnipotence, are ordered toward reason.  And in that humble way, we may find truth.