Lily Ponds and Diving Boards| Cornelius Van Til and C.S. Lewis’s Transcendental Arguments

As most of my readers already know, when it comes to Cornelius Van Til I’m pretty much a sycophant. But, As an evangelical Christian apologist, I also have to read C.S. Lewis on the regular and quote him at least once in all of my papers and blog posts. These two guys are my dudes. Although they were contemporaries, they never knew each other and if they had, they most likely would not have got along very well[1]. Van Til, the staunch Calvinist of Calvinists and Lewis, the low church “mere Christian” with Arminian leanings (to say the least) would have had deep theological rifts to battle over (see my post on the Euthyphro Dilemma).

But despite their disparate theologies, I’ve found some common ground when it comes to their philosophy- at least concerning their transcendental arguments.
In this post I want to briefly describe transcendental arguments in general then expound on one of Van Til’s and then one of Lewis’s discursive and intuitive transcendental arguments in hopes of cross-pollination- those of you who don’t like the other thinker might gain some appreciation for their thought. If any of the aforementioned words freaked you out, have no fear, all will be explained.

Those familiar with Van Til will not be surprised to find his name in close proximity with ‘transcendental’ language but those more familiar with Lewis might be taken aback. There certainly has not been as much written on Lewis and transcendental arguments (TAs from now on)- a problem that I’ve sought to remedy (C.S. Lewis’s TA for God).
For those unfamiliar with TAs, the word transcendental might seem daunting or even oddly mystical but it’s not so bad upon quick reflection. In explaining the word transcendental in TAs philosopher Roger Scruton, says “An argument is transcendental if it ‘transcends’ the limits of empirical enquiry, so as to establish the a priori conditions of experience.”[2] So a TA starts with some aspect of our human experience which is taken as an uncontroversial or incontrovertible “given” and asks, “given X (an aspect of human experience) what must be true?”

The TA proponent then seeks to show that a presupposition or precondition of X is Y, Y being something that their interlocutor is skeptical about. The goal is to move from the reality of the given, X, to the reality of the presupposed yet more controversial Y. If we all know that X exists, but X presupposes Y, then we ought to affirm, indeed we must affirm that Y also exists given X[3]. Put more succinctly, Van Til says, “A truly transcendental argument takes any fact of experience which it wishes to investigate, and tries to determine what the presuppositions of such a fact must be, in order to make it what it is.”[4]

Since there are at least four different ways to classify a TA, a further excursus down this rabbit trail will prove beneficial for analyzing Lewis and Van Til’s TAs. When it comes to the strategy of a TA, the ‘starting point’ sets up the force of the argument making them either deductive or retorsive. A deductive TA is the weaker of the two in that it takes an agreed upon given, one that both the proponent and the skeptic accept, and moves to the transcendental claim from there. Given the agreed upon axiom, you deduce the precondition. For instance, one might start a deductive TA with the starting point (L) language can truly map onto reality so as to describe it as it really is. For this to be forceful, the skeptic or the target of the TA, would need to agree with (L). What makes this the weaker form of TA is that the starting point has to be held in common between believer and skeptic alike. Thus to avoid the thrust of the deductive TA the skeptic might simply bite the bullet and deny (L).[5]

A retorsive TA, on the other hand, is the more powerful of the two because if successful, it would prevent the skeptic from denying the given thus forcing the skeptic to entertain the TA. According to TA theorist Robert Stern, “such arguments have been called “retorsive” from the Latin “retorquere”, meaning to twist or bend back, referring to the way in which such arguments “turn back” the sceptics own position against her.”[6] A quick google search indicated that retorquere is also the same root of ‘retort’. So a retorsive starting point of a TA is one that will turn or twist or bend back on the skeptic if they try to deny it. A good example of a retorsive TA comes from Aristotle’s defense of the fundamental law of logic known as the Law of Noncontradiction[7] in his Metaphysics. While the Law of Noncontradiction cannot be proven through direct argument such as using a modus ponens (if A then B, A, therefore B)- since any argument must presuppose the Law of Noncontradiction- it can be proven indirectly since argumentation is possible and a precondition of argumentation is the Law of Noncontradiction.[8]

  1. Argumentation is possible
  2. Argumentation presupposes the Law of Noncontradiction
  3. Therefore the Law of Noncontradiction obtains

This TA is retorsive in that the skeptic cannot deny premise I, for in denying it, they are arguing against it, showing that argumentation is in fact possible.

So we have distinguished between deductive and retorsive TAs but we can also distinguish between positive and negative TAs. A positive TA is basically what we have been describing thus far: you take the deductive or retorsive given of human experience and you argue positively in favor or the desired precondition in order to prove or establish that your position is correct. A negative TA on the other hand, takes the deductive or retorsive given and argues from the given against one of your interlocutors positions which run contrary to the given. Stated differently, in a negative TA you pit an objective presupposition- which we agree on or are forced to hold- against one of your opponent’s subjective presuppositions in order to refute said subjective presupposition. Philosopher James Anderson states it well, “a negative transcendental argument tries to show that an opposing viewpoint can only be believed and expressed on the assumption that it is in fact false.”[9] A great example of a negative TA comes from the late Greg Bahnsen when he described a debate on the existence of air. The debater arguing against air shows that his argument is absurd as he breathes in air and breathes it out in the form of his argument.[10]

We have now considered deductive, retorsive, positive, and negative categories of TAs. We are now free to consider Van Til and Lewis’s positive retorsive transcendental arguments. While we have several options to choose from in either man’s corpus, I have decided to pick arguments based on Immanuel Kant’s two qualifications for clarity. Kant says “…as to clarity, the reader has a right to demand not only what may be called discursive (logical) clarity, through concepts, but also an intuitive (aesthetic) clarity, through intuitions, i.e., through examples of other concrete illustrations.”[11] This will become more clear as we apply it.

Van Til employed discursive and intuitive clarity as a professor of apologetics, so most of his writings are geared at the meta-level so as to exhort his students to use transcendental arguments and reasonings, while he himself spent very little time (in comparison) actually setting forth a transcendental argument. C.S. Lewis on the other hand, a professor of Medieval literature, took up the mantle of public apologist from G.K. Chesterton and as such he spent much of his time and efforts ‘doing’ apologetics and almost no time talking about method and theory. With this in mind we can view Van Til as the Teacher and Lewis as the Practitioner- at least concerning discursive and intuitive positive-retorsive TAs. With that jargon in mind, let’s look at the teacher’s Diving Board Analogy from his book, A Survey of Christian Epistemology.


“As a help to clarification of this subject we may perhaps suggest a distinction between an immediate and an ultimate starting point. By an immediate starting point is meant the place where the knowledge of facts must begin. It is of course quite consistent with a theistic position to say that we must start with the “facts” as that term is understood ordinarily. Neither Augustine nor Calvin would have objected to saying that knowledge of self was their immediate and temporary starting point. But when the question of an ultimate starting point is raised the matter is different. In that case Augustine and Calvin would both have to say that their ultimate starting point is God. That is, they could intelligently think of their own non-existence but were unable to think intelligently of God’s nonexistence.”[12]


“Suppose a diver was standing on the tip of a diving board and that all that he could see of the diving board was the very tip on which he was standing. Suppose further that all that he could see around him was water. Now if he should say that the very spot from which he was about to make his leap is his starting point he might mean either of two things. If we thought of him as unaware of the connection of the point on which he was standing with the foundation on which it rested he would be speaking of that particular spot as the permanent or ultimate starting point. On the other hand, if he were fully aware of the fact that the tip of the diving board is only a tip of a board that rests upon a solid rock under water, he might speak of that tip as a starting point but only as an immediate starting point. The real and ultimate starting point for him would be the foundation on which the whole diving board was resting.”[13]

What Van Til makes discursively clear through his proximate/ultimate starting points and intuitively clear through his diving board analogy is that intelligible human experience presupposes God. Though we must “start” with our experience (in a retorsive sense), ultimately God stands as the necessary precondition of intelligibility just as a diver on the tip of a diving board presupposes a firm foundation which undergirds said diving board. This meta-argument, Van Til argues, can be applied to any aspect of human experience, including facts, self-consciousness, predication, knowledge, reason/rationality, and even empirical observation. It is because God is our ultimate starting point that Van Til says “we hold that the so-called “facts” are wholly unintelligible unless the supreme fact of God be brought into relation with them. We are willing to start with any fact as a proximate starting point, but refuse to admit before the investigation has begun that there can be no such fact as God.”[14] While the proximate/ultimate meta-argument has a scope as broad as our human experience, Van Til has left the work of actually setting forth TAs to his students and followers (check out my attempts at applying his argument to reason and facts).

Now, that’s all well and good, but you might be thinking “assertion is not demonstration. How exactly does our experience presuppose God?” Well, we have heard the meta-TA from the Teacher, now let’s hear a TA from the Practitioner, C.S. Lewis. While Lewis wasn’t intentionally following Van Til’s instructions, in chapter four of his Miracles, Lewis sets up an interesting positive retorsive TA for God from Reason on the heels of his negative retorsive TA against naturalism in chapter three.


“One man’s reason has been led to see things by the aid of another man’s reason, and is none the worse for that. It is thus still an open question whether each man’s reason exists absolutely on its own or whether it is the result of some (rational) cause- in fact, of some other Reason. That other Reason might conceivably be found to depend on a third, and so on; it would not matter how far this process was carried  provided you found Reason coming from Reason at each stage. It is only when you are asked to believe in Reason coming from non-reason that you must cry Halt, for if you don’t, all thought is discredited. It is obvious that sooner or later you must admit a Reason which exists absolutely on its own. The problem is whether you or I can be such a self-existent Reason.

This question almost answers itself the moment we remember what existence ‘on one’s  own’ means. It means that kind of existence which Naturalists attribute to the ‘whole show’ and Supernaturalists attribute to God. For instance, what exists on its own must have exited from all eternity; for if anything else could make it begin to exist then it would not exist on its own but because of something else. It must also exist incessantly: that is, it cannot cease to exist and then begin again. For having once ceased to be, it obviously could not recall itself to existence, and if anything else recalled it it would then be a dependent being. Now it is clear that my Reason has grown up gradually since my birth and is interrupted for several hours each night. I therefore cannot be that eternal self-existent Reason which neither slumbers nor sleeps. Yet if any thought is valid such a Reason must exist and must be the source of my own imperfect and intermittent rationality. Human minds, then, are not the only supernatural entities that exist. They do not come from nowhere. Each has come into Nature from Supernature: each has its tap-root in and eternal, self-existent, rational Being, whom we call God.”[15]


“In a pond whose surface was completely covered with scum and floating vegetation, there  might be a few waterlilies. And you might of course be interested in them for their beauty. But you might also be interested in them because from their structure you could deduce that they had stalks underneath which went down to roots in the bottom. The Naturalist thinks that the pond (Nature- the great event in space and time) is of an indefinite depth- that there is nothing but water however far you go down. My claim is that some of the things on the surface (i.e. in our experience) show the contrary. These things (rational minds) reveal, on inspection, that they at least are not floating but attached by stalks to the bottom. Therefore the pond has a bottom. It is not pond, pond for ever. Go deep enough and you will come to something that is not pond- to mud and earth and then to rock and finally the whole bulk of Earth and the subterranean fire.”[16]

In similar fashion to Van Til’s diving board analogy, Lewis argues that just as you can affirm from a lily pad that the pond has a bottom, so you can affirm that the existence of rational minds (of which you are one) presupposes a Rational Creator God. Lewis demonstrates the force of his TA with an interesting, almost cosmological, argument from rational causation. Reason comes from Reason, so if we are able to reason at all, then we must have been created by a self-existent Rational Being. While I’ve isolated this positive TA out from chapter four of Lewis’s book, he deals with the naturalist’s objection that reason can come from non-reason in chapter three where he employs a negative retorsive TA from reason against naturalism.

While I hope to tweak and defend these two arguments at a later time, the goal of this post was merely to lay out two discursive and intuitive TAs from two of my heroes. Van Til and Lewis were miles apart on various important points of theology and philosophy, but at the point of TAs, I think their thoughts converge. In viewing Van Til as the Teacher and Lewis and the Practitioner, the Christian apologist and philosopher can learn much.

Bonus intuitive TAs:

In Augustinian fashion, Van Til, Lewis, and G.K. Chesterton use Sun analogies as a kind of indirect argument approaching an intuitive TA. They argue in indirect fashion that just as you may know that the sun has risen by looking out and seeing the world illumined, so you can see the existence of God in the way He illumines your worldview.

Van Til: “With Augustine it must be maintained that God’s revelation is the Sun from which all other light derives. The best, the only, the absolutely certain proof of the truth of Christianity is that unless its truth be presupposed, there is no proof of anything. Christianity is proved as being. The very foundation of the idea of proof itself.” The Defense of the Faith, 4th ed., 381.

Lewis: “I believe in Christianity as I believe that the sun has risen, not only because I see it, but  because by it I see everything else.” “Is Theology Poetry?” in The Weight of Glory, 140.

G.K. Chesterton: “The Whole secret of mysticism is this: that man can understand everything by the help of what he does not understand. The morbid logician seeks to make everything lucid, and succeeds in making everything mysterious. The mystic allows one thing to be mysterious, and everything else becomes lucid.”

“The one created thing which we cannot look at is the one thing in light of which we look at everything. Like the Sun at noonday, mysticism explains everything else by the blaze of its own victorious invisibility.”

“But that transcendentalism by which all men live has primarily much the position of the sun in the sky.” Orthodoxy, 48.

(In the above quotes, Chesterton takes on the criticism that Christianity is mystical or mysticism since at the center of Christian theology is an incomprehensible God. He simply embraces the charge are runs with it.)


[1] They did not know each other personally.

[2] Roger Scruton, Kant: A Very Short Introduction (Oxford: Oxford University Press, 2001) 33.

[3] famous TA theorist Robert Stern explains : “As standardly conceived, transcendental arguments are taken to be distinctive in involving a certain sort of claim, namely that X is a necessary condition for the possibility of Y—where then, given that Y is the case, it logically follows that X must be the case too. Moreover, because these arguments are generally used to respond to skeptics who take our knowledge claims to be problematic, the Y in question is then normally taken to be some fact about us or our mental life which the skeptic can be expected to accept without question (e.g., that we have experiences, or make certain judgements, or perform certain actions, or have certain capacities, and so on), where X is then something the skeptic doubts or denies (e.g., the existence of the external world, or of the necessary causal relation between events, or of other minds, or the force of moral reasons). In this way, it is hoped, skepticism can be overturned using transcendental arguments that embody such transcendental claims.” Stern, Robert, “Transcendental Arguments”, The Stanford Encyclopedia of Philosophy (Summer 2019 Edition), Edward N. Zalta (ed.), URL = <;.

[4] Cornelius Van Til, A Survey of Christian Epistemology (Phillipsburg, Presbyterian and Reformed Publishing Co. 1980) 10.

[5] While this scenario is a deductive TA, I think it can quickly become a retorsive TA if the TA proponent merely asks the skeptic if their rejection of the starting point, language maps onto reality, itself maps onto reality. If so then they’ve refuted their objection and shown the inescapability of the now retorsive starting premise. If not, then the skeptic’s objection does not map onto reality- so why listen?

[6] Robert Stern, “Silencing the Sceptic?” in Transcendental Arguments in Moral Theory, ed. Jens Peter Brune, Robert Stern, Micha H. Werner (Berlin/Boston: Walter de Gruyter GmbH, 2017) 11.

[7] Formerly called “the Law of Contradiction*”

[8] “Aristotle’s “elenctic refutation” has been fruitfully compared to a Kantian transcendental argument. Transcendental arguments generally run as follows: If certain aspects of experience or thinking are possible, the world must be a certain way. Since these aspects of experience or thinking do exist, the world is a certain way. These aspects of our experience or thinking presuppose that the world is a certain way. That the world is a certain way explains these aspects of our experience or thinking and not the other way round. On this interpretation, Aristotle would be arguing that the world conforms to PNC, or that PNC is true, because it is presupposed by and explains the opponent’s ability to say something significant.” Gottlieb, Paula, “Aristotle on Non-contradiction”, The Stanford Encyclopedia of Philosophy (Spring 2019 Edition), Edward N. Zalta (ed.), URL = <;.

[9] from his lecture #10 Presuppositionalism in Practice – The Transcendental Argument in his RTS Christian Apologetics course on the RTS app.

[10] Also referenced in James Anderson’s lecture #10 cited above.

[11] Immanuel Kant, Critique of Pure Reason, Axvii, xvii. Bold original.

[12] Cornelius Van Til, A Survey of Christian Epistemology, 120.

[13] Ibid.

[14] Ibid., 202.

[15] C.S. Lewis, Miracles, 41-43.

[16] Ibid., 45.


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