If your mind is only moving molecules, why would you trust a single thing it tells you?
Philosophical naturalism is the belief that nature is all there is — that matter and energy, governed by physics and shaped by chance over time, exhaust the whole of reality. No God. No soul. No realm above the physical. It is sold today as the hard-headed, grown-up view, the position of someone who has put away comforting stories and faced the cold facts. And it has a problem so deep that it cannot survive its own first sentence. Naturalism, taken seriously, cannot account for the very reasoning it uses to argue for itself. It saws off the branch it is sitting on.
Let me show you the cut, and then let me show you what is actually holding the branch up.
The argument from reason
Start with a question the naturalist rarely asks himself: what is a thought? On strict naturalism, a thought is a brain state — a particular arrangement of neurons firing, fully produced by prior physical causes. Chemistry in, chemistry out. Every belief you hold, including the belief that naturalism is true, is the end product of a long chain of physical events that were going to happen regardless of whether the belief was correct.
Now feel the weight of that. Physical causes are not aimed at truth. A neuron does not fire because a conclusion is valid; it fires because the prior physical state made it fire. But reasoning is a completely different kind of thing. When you reason, one thought leads to another because it logically follows — the connection is rational, not merely chemical. If your every conclusion is just the next domino falling, then you are not reasoning at all. You are only experiencing the sensation of reasoning while physics does what physics was always going to do.
This is the heart of what has been called the argument from reason, pressed by thinkers from C. S. Lewis to Alvin Plantinga. Lewis put the knife in cleanly: a train of thought has value only if it is determined by reasons and truth, not merely by causes. If naturalism is true, all our thoughts are determined by non-rational causes. Therefore, if naturalism is true, we have no reason to trust our thoughts — including the thought that naturalism is true. The position refutes itself. It claims to be the conclusion of careful reasoning while denying that careful reasoning, in any truth-tracking sense, can exist.
Evolution does not patch the hole
The usual reply is that natural selection would have tuned our brains for truth, because creatures with accurate beliefs survive better. But selection does not care about truth; it cares about behavior that survives. As Plantinga argued, what gets passed on is conduct that works, not belief that is correct — and a great many false beliefs can produce perfectly survival-friendly behavior. A creature that believes the predator is a friend best fled from, for entirely wrong reasons, runs just as fast as one who has the facts straight. Selection sees the running. It is blind to the belief behind it.
So evolution-plus-naturalism gives you brains tuned for fitness, with no guarantee — and on its own terms, no way to get a guarantee — that fitness and truth line up. The branch is still cut. You cannot use a faculty to certify itself when the only story you have told about that faculty gives you no reason to trust it.
It is not only reason — it is morality and logic too
The same collapse happens everywhere the naturalist tries to stand. Take the laws of logic — the law of non-contradiction, say, that a thing cannot both be and not be in the same way at the same time. That law is not made of matter. It does not have a location or a mass. It holds everywhere and always, and it held before any brain existed to think it. Where does an immaterial, universal, unchanging law come from in a universe that is supposed to be nothing but particles in motion? The naturalist uses logic in every argument and cannot, on his own worldview, say what logic is or why it should govern reality.
Morality fares no better. If we are rearranged stardust, then “you ought not torture children” is, at bottom, a feeling that evolved because it helped our ancestors’ genes — no more binding on reality than a preference for sweet over bitter. Yet no one actually lives as though cruelty were merely unfashionable. We know some things are truly wrong, wrong whether or not anyone feels it, wrong even if the whole tribe approves. That knowledge of real, objective moral obligation is a fact every person reasons from and no materialism can ground. You cannot get an ought from atoms.
Where reason, logic, and morality actually live
Here is the turn. The Christian is not embarrassed by reason, logic, and moral law — he expects them. They are exactly what you would predict if the universe is the work of a rational, moral Mind rather than mindless matter. Scripture opens not with stuff but with a speaking God, and John tells us what stood at the beginning:
In the beginning was the Word, and the Word was with God, and the Word was God. He was in the beginning with God. All things came into being through Him, and apart from Him nothing came into being that has come into being. (John 1:1–3)
The Greek behind “Word” is Logos — reason, rationality, the rational ordering principle of all things. Christianity claims that reason is not a late accident thrown up by matter; reason is woven into the foundation of reality because reality was made by a rational God. That is why the universe is intelligible, why mathematics describes it, why logic governs it, and why your mind — made in the image of that God — can think His thoughts after Him. Paul says we live in this God so deeply that even our reasoning depends on Him: “in Him we live and move and exist” (Acts 17:28). And the Psalmist gives the whole epistemology in one line: “in Your light we see light” (Psalm 36:9).
The suppressed knowledge
So why do brilliant people hold a view that undercuts itself? Paul answers that too, and it is not flattering to any of us:
For the wrath of God is revealed from heaven against all ungodliness and unrighteousness of men who suppress the truth in unrighteousness, because that which is known about God is evident within them; for God made it evident to them. … For even though they knew God, they did not honor Him as God or give thanks, but they became futile in their speculations, and their foolish heart was darkened. Professing to be wise, they became fools. (Romans 1:18–22)
Naturalism is not finally a failure of intelligence. Some of its defenders are formidably smart. It is a worldview that must borrow what it cannot own — using reason, logic, and moral outrage that only make sense in a God-made universe, in order to deny the God who made it. Every time the materialist argues, he proves the point against himself: he is appealing to truth that transcends matter while insisting nothing transcends matter.
The branch and the tree
You cannot saw off the branch you are sitting on and expect to stay in the air. Naturalism takes the saw to reason itself and then asks you to trust the conclusion. The honest move is to look down and notice what has been holding you up the whole time. The reliability of your mind, the authority of logic, the reality of right and wrong — these are not problems for the Christian. They are fingerprints. They are what a world looks like when it was spoken into being by the Logos, and they are quietly testifying, in every argument the skeptic makes, that he already knows more than his worldview will let him say.
Reason did not come from matter. Matter, and reason, and you, came from God.
Teaching the Word. Watching the Times.
— SmithForChrist