We live in a disenchanted world, and naturalism is the lens through which many people in the West view reality. As author Richard Beck explains:
Something dramatic has changed over the last five hundred years in the West, especially in our relationship to God. We live in a secular, technological world that has pushed God and the supernatural to the margins. Things our ancestors took as manifestly obvious we now reject . . . Our world is disenchanted. Science has replaced superstition. To be sure, religious belief hasn’t vanished . . . [but] people today do regularly doubt the existence of God, and rates of atheism and agnosticism continue to climb. We demand hard facts, data, and evidence. We revel in skepticism. Nothing is true for us until a scientist shows up.1
There are different varieties of naturalism, but the one that arguably predominates in the West is the view that “the spatio-temporal universe of physical objects, properties, events, and processes that are well established by scientific forms of investigation is all there is, was, or ever will be.”2
One of the difficulties this kind of naturalism faces is that it implies determinism—“the view that every event or state of affairs is brought about by antecedent events or states of affairs in accordance with universal causal laws that govern the world.”3 So, if a heavy thunderstorm moves over my neighborhood, and lightning strikes a tree in my yard, causing it to fall on my driveway, that event was determined. If we could account for all of the physical interactions involved in this event, and the previous conditions that led to it, we could predict exactly when the tree would be struck, and where in my driveway it would fall.
From a naturalistic view, if we know all the physics and natural laws involved in any given situation, we can predict what will happen with certainty. Nothing outside the universe and its regularities can interfere with the predictable cause and effect of events.4
One counterintuitive implication of this, however, is that human thoughts, feelings, and behaviors are also determined. Like rocks and trees, humans are subject to physics and natural laws, and these determine what happens inside our brains, which in turn determines what we think and do.
Some naturalists attempt to evade this conclusion, since it effectively robs humans of free will, but many readily embrace it.5 The notable new atheist and neuroscientist Sam Harris writes, “Free will is an illusion. Our wills are simply not of our own making. Thoughts and intentions emerge from background causes of which we are unaware and over which we exert no conscious control. We do not have the freedom we think we have.”6
Philosopher Paul Churchland states, “the human species and all of its features are the wholly physical outcome of a purely physical process.”7
Philosopher Alex Rosenberg writes, “We can be sure of a great deal about how the brain works because the physical facts fix all the facts about the brain. The fact that the mind is the brain guarantees that there is no free will. It rules out any purposes or designs organizing our actions or our lives.”8
The late Cornell professor William Provine asserted, “There are no gods, no purposes, and no goal-directed forces of any kind . . . and no free will for humans, either.”9
While such thinkers seem happy to embrace the idea that what goes on in our minds is determined by forces “over which we exert no conscious control,” they neglect to accept that this includes our reasoning and beliefs. But if that’s the case, why should we trust anything our reason tells us?
If we witnessed an avalanche, and the rocks falling to the bottom of the mountain spelled out “rest stop ahead,” would we believe the message and look for the rest stop?
C. S. Lewis believed this implication of naturalism made it untenable, and expounded the argument in his book Miracles: A Preliminary Study.10 The argument has since come to be known as the Argument from Reason (AFR).11
The Argument from Reason
For the sake of brevity, I’ll formulate Lewis’s AFR in a series of brief statements, and cite thinkers who expand on the propositions, especially Lewis and philosopher Victor Reppert, a leading proponent of the argument.12
1. No belief is rationally inferred if fully explained by non-rational causes.
As we saw in the avalanche illustration, non-rational causes (the rocks falling into patterns that look like words) can’t produce rationality (a reliable message about a rest stop).
Lewis put it this way: “If my mental processes are determined wholly by the motions of atoms in my brain [non-rational causes], I have no reason to suppose that my beliefs are true . . . and hence I have no reason for supposing my brain to be composed of atoms.”13
Similarly, Reppert observes: “Rational beliefs must . . . have rational causes, but naturalism holds that, in the final analysis, all causes are non-rational causes. But if this is so, then human beings really don’t reason.”14
2. If naturalism is true, all beliefs are fully explained by non-rational causes.
Recall Paul Churchland’s statement earlier that “the human species and all of its features are the wholly physical outcome of a purely physical process.” No physical process thinks, reasons, or draws conclusions, so these processes are non-rational. There are no thinking atoms, molecules, or chemical reactions. This is why we can’t trust the “words” created by an avalanche—because it’s a purely physical, non-rational, purposeless event.
Atheist philosopher Bertrand Russell thus declared that man’s “origin, his growth, his hopes and fears, his loves and his beliefs, are but the outcome of accidental collocations of atoms.”15
Reppert notes, “If [naturalism] is true, the appearance of believing something for a reason is just that—appearance. . . . The blind physical processes of physics [cause our “conclusions”], and the claim to have inferred anything is an illusion.”16
3. Therefore, if naturalism is true, no belief is rationally inferred.
This follows logically—if beliefs are non-rational, they can’t be rationally inferred.
4. We have good reason to accept naturalism only if it’s rationally inferred from evidence.
Any asserted idea needs rational support. In Lewis’s words, “All possible knowledge . . . depends on the validity of reasoning.”17 How can we hold any belief without the ability to use reason to arrive at that belief?
5. Therefore, there is not, and cannot be, a good reason to accept naturalism.
Naturalism is a self-refuting position because it entails that the ideas we hold, including naturalism, result from irrational processes. Thus, we cannot trust what our reason tells us.
In the same way that we can’t believe the message created by the avalanche, we can’t believe in naturalism, because blind physical processes brought both ideas about.
Lewis writes, “no account of the universe can be true unless that account leaves it possible for our thinking to be a real insight. A theory which explained everything else in the whole universe but which made it impossible to believe that our thinking was valid, would be utterly out of court.”18
To this point, the argument has shown that naturalism undermines rationality. Adding two further steps, we can argue that God is the best explanation for our reasoning ability.
6. Many human beliefs are rationally inferred.
We know this from our everyday experience. We know we can reason from facts to conclusions. For example, we can see dark clouds and infer that it’s about to rain.
7. Therefore, human reason must come from a rational source beyond nature, and God is the most reasonable source.
As Lewis observed, “The Naturalists have been engaged in thinking about Nature. They have not attended to the fact that they were thinking. The moment one attends to this it is obvious that one’s own thinking cannot be merely a natural event, and that therefore something other than Nature exists.”19
Reppert provides a helpful explanation of this final step in the argument:
According to theism, the universe is a rational place because it is the creation of a rational being, namely God. Reason is, so to speak, on the very ground floor of reality. Given that God creates creatures, it is [at] least possible that God might wish to provide those creatures with some measure of the rationality which God himself possesses. And human beings reflect God’s rational character by having the capacity [to] think logically.20
Thus, the Christian worldview provides very hospitable soil for accounting for our ability to reason and the validity of our reasoning. Naturalism, on the other hand, makes reason the result of non-rational processes that can’t be trusted. Therefore, our ability to reason and obtain knowledge is a good reason to embrace Christian theism but reject atheistic naturalism.
Christopher L. Reese (MDiv, ThM) is the founder and editor of The Worldview Bulletin and a general editor of the Dictionary of Christianity and Science (Zondervan) and Three Views on Christianity and Science (Zondervan). He is the author of 100 Old Testament Quotes by Jesus: How Christ Used the Hebrew Scriptures (Rose/Tyndale), and his articles have appeared in Christianity Today, The Christian Post, Bible Gateway, Beliefnet, the C. S. Lewis Institute, and other sites.