There are several points of difference between the Classical and Presuppositional models of apologetics. One of them has to do with a logical fallacy. In common language we call this “circular reasoning,” though its technical term is the petitio principii fallacy. This error assumes in one’s premise what is to be demonstrated in one’s conclusion. 

Supposing someone challenged my trustworthiness as a witness in court, and on those very grounds my actual identity as stated in words and in recent records. It would do no good for me to protest, “Your honor, ladies and gentlemen of the jury—C’mon, it’s me. I am sitting right here!” Of course I would be sitting right there. But doubt was not raised as to the empirical state of my body. It was specifically a question of what I have been claiming as to my personal identity.

My appeal to believe me on the grounds that I am the one saying it has begged the whole question as to the relevant meaning of “I” in this case. I am being challenged to prove that I am who I have been saying that I am. In such a case, to simply repeat the “I” is to insert into my first premise what they really need to hear as a reasonable conclusion. 

Now this all may seem out of the ordinary for us. But many Christians will resort to “demonstrating” the existence of God by simply asserting things already taken for granted to be His effects. Others will “establish” the Bible by starting from the premise that it is God’s word. As a classical apologist, I certainly agree that many effects of God can establish His existence and that the divine inspiration and authority of Scripture can be established. But it is a very sloppy and simplistic defense of the faith to argue for these things in a way similar to how I appealed to the judge and jury above.

We cannot argue in a circle and expect people to find it reasonable. This is the logical version of putting the cart before the horse. In a valid and persuasive argument, premises should be better known than conclusions. That is the whole point of having conversations aimed at persuasion. One person brings another to a position that is less familiar to them (perhaps they are downright resistant to it) on the basis of some position they already have in common. 

Presuppositionalism and Circular Reasoning

Advocates of presuppositionalism will attempt to say that “All human reasoning is circular.” It functions as a reason to deny that we need to make arguments from commonly accepted premises (in straight lines) to conclusions. One of their proponents, John Frame, puts it in this way. An empiricist will only accept conclusions that answer to empirical verification. A rationalist will only allow what follows certain axioms of the mind. A Muslim will only proceed from what the Qu’ran rules on. And so on with other views.1

Greg Bahnsen put the same thing this way:

"Ultimately, then, the details of one's theory of knowledge are 'justified' in terms of their coherence within the distinctive and broad theory of which they are a part."2

Such ultimate “circles” are not “vicious circles,” we are assured. That is, they do not avoid arguments by merely restating in the conclusion what is already there in the premises. They simply proceed the only way one can. Eventually one will always “circle back” to fundamental commitments that cannot be gotten behind. Hence some will call this a “virtuous circle.”

But there is something fishy going on here. Surely the bare act of recognizing someone’s ultimate presuppositions (and that everybody has them) is not the same as formally asserting them as a premise when it is the whole question that is being begged. From the perspective of classical apologetics, calling the former “circularity” is misleading.

For example, moving back to those ultimate commitment circles of the empiricist or Muslim, the question is whether those ultimate commitments can be queried and known as to whether or not they are true. If not, there is no objective reason standing over us all, by which we can tell that the Muslim claims about his book are any less reasonable than ours. Both claim, “Because God says so.” The presuppositionalist has given himself no recourse in such conversations, which is the whole fabric of apologetics.

Someone may still object, “But what is really wrong with this ‘broader’ kind of circularity?” In the first instance, it is nothing to the point and proves too little. If all the presuppositionalists mean by this “circle” is that “All worldview-holders only hold to both premises and conclusions that they see to be consistent with that worldview,” then it is certainly true, but hardly worth saying. Who would not agree with this?

But there may be a larger problem for them. M. Dan Kemp makes the case that more broadly circular arguments can actually be absurd and even deceptive, even if not formally invalid. There are actually times when proper inferences can be made when there is question-begging going on in one’s premises. By itself, that does not make an argument invalid (Decomposition is one example: i.e. P · Q, ∴ P). However, if one was to argue: P → Q, Q → R, R → S, S → P, ∴ P, such arguments, Kemp says, are

“worse arguments because they violate rational norms by doing a better job than narrow circular arguments of appearing to establish a conclusion without doing so.”3

In other words, they are actually a form of deception, even if self-deception.

There is a most essential problem with the appeal to circular reasoning. It is really very simple. Why should one prefer the Christian circle over the Buddhist circle or the Atheist circle or the Postmodern circle? Or, to put it more literally, what is better and more reasonable about taking one’s stand in Scripture as opposed to taking one’s stand in the Qur’an or in the Book of Mormon? Whatever one’s answer, the presuppositionalist circle is broken. Unless one wants to be utterly consistent and reply, “Well, there is no such reason.” But surely the presuppositionalist would not want to admit defeat in this way. The presuppositionalist appeal to valid circular reasoning functions the same way that everything else in presuppositionalism does. It is an argument that no rational arguments are required. It is fideism dressed up in Calvinistic garb. 

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1. cf. John Frame, The Doctrine of the Knowledge of God (Phillipsburg, NJ: Presbyterian & Reformed Publishing, 1987), 130.

2. Greg Bahnsen, Van Til's Apologetic (Phillipsburg, NJ: Presbyterian & Reformed Publishing, 1998), 482.

3. M. Dan Kemp in David Haines, ed., Without Excuse: Scripture, Reason, and Presuppositional Apologetics (Leesburg, VA: Davenant Press, 2020), 23.