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C. S. Lewis’s Argument from Reason

The Promise of Natural Theology

I am intellectually indebted to a brilliant Christian thinker from the twentieth century who taught me how to defend the Christian faith. He taught me how to prove the supernaturalism of Christianity by proving—you might say—the impossibility of the contrary. That is to say, he taught me not only that supernaturalism is a credible belief, but also that its denial is downright incredible, since naturalism (supernaturalism’s alternative) cannot attempt to prove anything without contradicting itself. This thinker showed not only that reason helps us to weigh arguments for the existence of God; he helped me to see how reason, indeed, is an argument for the existence of God.

Now, at this point, I could forgive the informed reader for assuming that the figure I am describing is the late, great, Dutch-American theologian, Cornelius Van Til (1895-1987), but he would be wrong. I have been describing C.S. Lewis (1898-1963). To be sure, Van Til taught all of these things as well, and I owe him a debt of gratitude for reinforcing these lessons, but Lewis gets credit for introducing them to me, and for showing me what they look like in a number of literary settings. In this essay, I shall consider Lewis’s argument from reason. Contrary to what some modern reformed thinkers may insist, this feature is not a unique contribution by Van Til or the “presuppositional” school of apologetics he pioneered. While Van Til was a valiant defender of this argument (or something very much like it, which has come to be known as the “transcendental argument”), and while he did bring in some creative subversions in his deployment of this argument against Kantian idealism, he was not its originator, nor even its best practitioner. Additionally, while some modern presuppositionalists may appeal to the argument as a kind of alternative to natural theology, I will show how Lewis puts it to use as a natural theological argument.

The Matter of Anscombe and the fate of “the Argument from Reason”

Reason—the reason of God—is older than Nature, and from it the orderliness of Nature, which alone enables us to know her, is derived. Click To Tweet First, a very brief aside. It would be very easy on this article about Lewis’s argument from reason to divert our attention into a no doubt fruitful, but nevertheless distracting, rabbit trail. Now, I for one, am a great lover of the personal essay precisely because of its meandering feature. In fact, after briefly extrapolating Lewis’s argument from reason in his apologetic work, Miracles, I think I shall indulge myself in some good-spirited meandering. But such a romp through the wilderness of my imagination will not take me into the forest we might label “the Anscombe affair,” nor in the prairies of “contemporary articulations of the argument.” This failure to venture that far off my well-trodden thought-paths is owing chiefly to the fact that, so far as my own imagination goes, these areas are rather barren. I do not feel I am well-versed on either of these areas to do them any justice, even in the spirit of “meandering,” though I do feel comfortable enough to say this much: while it seems clear that Lewis was flatly defeated in his debate with the Catholic philosopher, Elizabeth Anscombe, when they argued over this very issue at the Oxford Socratic Club (which Lewis himself started), it seems equally clear that some of the accounts of this debate’s aftermath are overblown. Lewis did not cower from the realm of philosophy and hide in the safety of children’s fiction. Not only did he continue to engage in apologetics more broadly, he did not even relinquish this particular argument. Lewis revised the argument from reason in the second edition of his book, taking Anscombe’s criticisms on the chin and using the debate to sharpen, rather than forfeit, his argument.[1] It is Lewis’s strongest version of the argument I wish to interact with here. Which brings me to that other area I do not plan to touch on: the state of the argument from reason today, and whether it has been strengthened since Lewis. That is a question I leave to others.[2]

The Argument from Reason

For Lewis, the argument from reason was developed within a much larger argument in defense of the Christian affirmation of miracles specifically, and Christianity more broadly. The argument is laid out in his third chapter, “The Cardinal Difficulty of Naturalism.” This particular leg of his argument endeavors to debunk naturalism, in favor of supernaturalism (both terms he defines for the reader in chapter two, “The Naturalist and the Supernaturalist”). This work of debunking will take several chapters, and each of them take on the same shape as this one in particular, though considered through the lens of different transcendentals. If the argument from reason debunks naturalism on the grounds of Truth—i.e., naturalism cannot account for reason without contradicting itself—the argument from morality (chapter five, “A Further Difficulty in Naturalism”) argues the same on the grounds of Goodness, and the argument from beauty (chapter nine, “A Chapter Not Strictly Necessary”) does the same on the grounds of Beauty. This is to be expected if God is one—the Good, the True, and the Beautiful to which our truthfulness, goodness, and beauty conform (see chapter eleven, “Christianity and ‘Religion’” and chapter fourteen, “The Grand Miracle”). But we are getting ahead of ourselves.

By the time chapter three rolls around, Lewis is only concerned with comparing the relative viability of two very broad outlooks, naturalism and supernaturalism. “If naturalism is true,” he says in his opening statement, “every finite thing or event must be (in principle) explicable in terms of the Total System.”[3] The caveats of this statement are important. Lewis is not saying that a naturalist must personally account for every finite thing or event. That’s where the “in principle” caveat comes in. Nor will Lewis go on to make the argument that naturalists cannot reason simply because reason is inexplicable in naturalism as a Total System—quite the opposite in fact. That’s where his second caveat comes in (i.e., “explicable in terms of the Total System”). The point is that since naturalism is predicated on a universal denial—the rejection of any supernatural cause for any finite thing or event, and therefore the denial that anything finite can be predicated on anything outside of the Total System of the natural world—it cannot allow even one exception without disproving itself. Lewis may seem harshly unfair to lay such a strict criterion on naturalism, but we must understand that naturalism does this itself. Naturalism, not Lewis, has made matters so challenging for naturalism.

So, how does naturalism fair under these terms? Lewis begins where any exploration of a system of belief must begin: the notion of reason. “Unless human reasoning is valid,” says Lewis,

no science can be true. It follows that 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. For that theory would itself have been reached by thinking, and if thinking is not valid that theory would, of course, be itself demolished. It would have destroyed its own credentials. It would be an argument which proved that no argument was sound—a proof that there are no such things as proofs—which is nonsense.[4]

In contrast to Van Til, rather than issuing a combative dare, Lewis instead opts for an invitation. Click To Tweet This, maintains Lewis, is precisely what naturalism does. For the rest of the chapter, Lewis considers various accounts of reason a naturalist might give, which would not violate the principle of naturalism itself (i.e., the notion that nothing beyond the system of nature exists), showing how they each amount to vain attempts to kick the can down the road. For example, Lewis considers the notion that reason is explicable as a result of informed inferences, based on repetitive experiences. This won’t work, according to Lewis, since “the assumption that things that have been conjoined in the past will always be conjoined in the future is the guiding principle not of rational but of animal behavior. Reason comes in precisely when you make the inference, ‘Since always conjoined, therefore probably connected’ and go on to attempt a discovery at that connection.”[5] In other words, inference cannot itself explain reason, because once inference is used to attempt to explain reason, it is itself the tool of reason and cannot itself give rise to reason. “If the value of our reasoning is in doubt,” says Lewis, “you cannot try to establish it by reasoning.”[6]

Toward the end of this chapter, Lewis makes reference to the explanatory power of Christianity, which he will develop far more earnestly in subsequent chapters. Here, however, Lewis simply invites his readers to consider how “the cardinal difficulty of naturalism” is no difficulty at all with theism, and in particular, Christian theism.

[The theist] is not committed to the view that reason is a comparatively recent development molded by a process of selection which can select only the biologically useful. For him, reason—the reason of God—is older than Nature, and from it the orderliness of Nature, which alone enables us to know her, is derived. For him, the human mind in the act of knowing is illumined by the Divine reason. It is set free in the measure required, from the huge nexus of nonrational causation; free from this to be determined by the truth known. And the preliminary processes within Nature which led up to this liberation, if there were any, were designed to do so.[7]

It is here that Lewis’s argument from reason moves from its polemic to its constructive form. No longer does he use it simply to undermine Christian theism’s starkest alternative (i.e., naturalism), he uses it to positively bolster up the trustworthiness of Christianity by showing the latter’s justification of reason. Not only does Christianity accord with reason, it accounts for reason. Therefore, this argument is not an alternative to natural theology. Rather, it is the natural theological justification for all natural theology, since “the preliminary processes within Nature which led up to this liberation, if there were any” (such as arguments of causation, cosmology, or teleology) “were designed to do this.”

But earlier, I gave some indication that there was some interplay between Lewis’s argument from reason and Van Til’s transcendental argument. Where might this interplay lie? This last question will take some teasing out.

There and Back Again: A Lewisian Journey

I think the first book I ever read from cover to cover was C.S. Lewis’s The Great Divorce. Like many eventual bookish Christians, my bookishness came about in precisely the opposite way as Lewis’s. Lewis developed his love for reading long before he ever converted to the Christian faith, and his large reservoir not only brought color and texture to his understanding of the Christian life after his conversion to Christ, but actually helped to lead him to Christ. For my part, I was never studious, and I never enjoyed reading. At least, not until after my conversion to Christ and my subsequent interest in apologetics. The first sign of this newfound appetite for learning came in the form of my reading The Great Divorce. As a young boy, my mother read the Narnia books to me and my siblings, but I was eventually made aware of the fact that Lewis had written non-fiction Christian literature, and indeed, Christian apologetics. I picked up The Great Divorce as a teenager, thinking it belonged to this non-fiction category and was probably about divorce (or perhaps the Fall of mankind, with “divorce” serving as the dominant metaphor), and was very confused for the first couple of chapters. By the time I finished the book, I had secured a lifelong relationship with it (which has only deepened in recent years as I return to it periodically while I “catch up” on reading its author’s classical influences, chiefly Dante) and its author. I never let a calendar year go by without reading a handful of Lewis’s books, and with every passing year, I am increasingly convinced of his prescience—it truly is all in Lewis, it’s all in Lewis! Bless me!Not only does Christianity accord with reason, it accounts for reason. Click To Tweet

While this lifelong relationship with Lewis has remained unbroken since that providential case of mistaken literary genre, it has certainly waxed and waned. The only serious season of declension came in the form of about five years spanning from my later college years into the majority of my time as an MDiv student in seminary. While I could never bring myself to disavow my love for Lewis, I did develop a pretentious snobbery: I had outgrown the pagan-standard-affirming apologetic of Lewis in favor of a new intellectual force in the person of Cornelius Van Til. I have written elsewhere about my season as a rabid presuppositionalist, foaming at the mouth and confirming every “cage-stage” stereotype in the book, so I won’t belabor the point here. Suffice it to say, I was bought-all-in on Van Til’s critique of Lewis and his “classical apologetic approach.” As much as I loved Lewis, I pitied him (quite patronizingly, I might add, to my shame), for his unfortunate blunder of forfeiting the debate for Christianity on the outset by granting to the pagan—the rebel, the one who occupies Christianity’s counterpoint on the antithesis—too much epistemologically authoritative ground. “Poor Lewis,” was my implicit thought, “a brilliant mind wasted on a bad methodology.”[8]

Again, I have already briefly described why this headlong plunge into Van Til and Van Tilianism had a start and end date, and I should be properly understood as a former Van Tilian (or, recovering Van Tilian), but where I have landed is where I have started: exasperated at my former conceited tisking at Lewis, throwing up my hands, and channeling all the spirit of Professor Kirk I can muster, saying: “it’s all in Lewis! All in Lewis! Bless me!” However, while I regret my former pretensions, I do not regret my Van Tilian excursus. Not only does Van Til making breathtakingly beautiful and profound observations in his own right, his “transcendental argument” has helped to elucidate Lewis’s “argument from reason” in ways I would not be privy to had I not immersed myself in his works—and gotten his logic into my DNA—over a matter of years.

Without minimizing the real differences between Van Til’s transcendental argument and Lewis’s argument from reason, I suggest that the two rhyme in deeply resonant and compatible ways. To use an analogy from the arts, consider Shakespeare’s description of imagination in A Midsummer Night’s Dream:

The poet’s eye, in a fine frenzy rolling,

Doth glance from heaven to earth, from earth to heaven;

And, as imagination bodies forth

The forms of things unknown, the poet’s pen

Turns them to shapes, and gives to airy nothing

A local habitation in time. (Act V, scene 1)

In his reflections on this Shakespearean verse, Malcom Guite writes,

The poet’s glance actively takes in both earth and heaven, sees them reciprocally and plays with their relationship. So we have both trajectories, “heaven to earth” and “earth to heaven.” Heaven and earth stand for the invisible and the visible worlds, the world we inhabit and seek to comprehend, and the world we can only apprehend imaginatively or by intuition.[9]

I never let a calendar year go by without reading a handful of Lewis’s books, and with every passing year, I am increasingly convinced of his prescience—it truly is “all in Lewis, it’s all in Lewis! Bless me!” Click To Tweet At the risk of stretching the comparison too far, we might say that Lewis’s argument from reason and Van Til’s transcendental argument are the same essential argument that runs along a similar axis to this one described by Shakespeare and Guite. Van Til argues deductively, from heaven to earth. Lewis argues inductively and abductively, from earth to heaven. When considering reason, Van Til issues a confident dare to the skeptic and the naturalists: “just try to account for reason given your own worldview’s premises. It’s all in vain, Christianity alone gives you what you need to make sense of reason.” To put the argument in a pithy and memorable form, Douglas Wilson famously posited the debate between naturalism and supernaturalism as bringing soda cans up on opposite debating podiums in lieu of debaters. Were we to shake them up, open their lids, and then judge the “correct” position based on which one fizzes more, we would not know how to answer the question. The absurdity is clear. But Wilson is right to point out that the naturalist is not far off from having to make a similar argument. If all there is is that which is explicable within the Total System of nature, arising from within nature herself, reason cannot be explained without being explained away. There is no place for actual reason within the system of “nothingbutery” that attempts to “explain” reason by describing its chemical, biological, and neurological accompaniments. If that’s all there is, there is no reason, and therefore no reason to take naturalism any more seriously than the notion that “blue is the smell of algebra, and much four bitter shoe.[10]

In contrast to Van Til, rather than issuing a combative dare, Lewis instead opts for an invitation: “consider, what accounts for reason? It does not seem that naturalism has the capacity. If naturalism cannot account from reason at all—and indeed, seems to undermine the notion of reason—mustn’t we conclude that naturalism cannot be true (or even reasonable)? If so, does that not imply that whatever does account for reason, it must be supernatural on some level?” While the Van Tilian will be quick to point out that “supernaturalist” does not a Christian make, we can only say that this is quite right, but not every argument must be the only argument.[11] This is an argument that, once established, naturally becomes a premise in service to many more specific arguments. In fact, any argument that does prove Christianity to be uniquely true must at least have this premise (i.e., reason’s soundness). In any case, one can see, I hope, the similarity between these two approaches. Both run a redactio ad absurdum to showcase how naturalism caves in on itself—it testifies to its own inadequacy and cries out for a more reasonable account of reason, which Christianity is eager to offer.


[1] For a fascinating account of this episode from Anscombe’s perspective, within the context of her philosophical convictions and academic career as a whole, see Benjamin J.B. Lipscomb, The Women Are Up to Something: How Elizabeth Anscombe, Philippa Foot, Mary Midgley, and Iris Murdoch Revolutionized Ethics (Oxford University Press: 2021), Chapter 6.

[2] See, for example, Victor Reppert, C.S. Lewis’s Dangerous Idea: In Defense of the Argument from Reason (IVP Academic: 2003).

[3] C.S. Lewis, Miracles (Touchstone: 1960), 20.

[4] Lewis, Miracles, 22.

[5] Lewis, Miracles, 30-31.

[6] Lewis, Miracles, 32.

[7] Lewis, Miracles, 34.

[8] This remains the implicit and explicit posture of some contemporary self-professing presuppositionalists, like Doug Wilson. I have written an appreciative review and critique of Wilson’s appreciative and critical reflections on Lewis here.

[9] Malcom Guite, Lifting the Veil: Imagination and the Kingdom of God (Square Halo Books: 2021), 19.

[10] Don’t try to decode this. It is nonsense on purpose.

[11] For a good example of an abductive presentation of Christianity, see Gavin Ortlund’s, Why God Makes Sense in a World That Doesn’t: The Beauty of Christian Theism (Baker Academic, 2021).

Samuel G. Parkison

Samuel G. Parkison (PhD, Midwestern Seminary) is Associate Professor of Theological Studies and Director of the Abu Dhabi Extension Site at Gulf Theological Seminary in the United Arab Emirates. Before coming to GTS, Samuel was assistant professor of Christian studies at Midwestern Baptist Theological Seminary, and pastor of teaching and liturgy at Emmaus Church in Kansas City. He is the author of Revelation and Response: The Why and How of Leading Corporate Worship Through Song (Rainer, 2019), Thinking Christianly: Bringing Sundry Thoughts Captive to Christ (H&E, 2022), and Irresistible Beauty: Beholding Triune Glory in the Face of Jesus Christ (Christian Focus, 2022).

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