Can Skeptics Justify their Foundations?

An Analysis and Commentary on My Live Exchange with a Skeptic

Near the end of a recent livestream, I had an exchange with an atheist caller that nicely illustrates a recurring problem in apologetic conversations. The discussion touched on sense perception, logic, causation, and induction, but the real issue was deeper than any one of those topics. The central question was this: can the skeptic justify the foundational beliefs he is already using in order to argue at all? That question, more than disagreements about evidence or arguments, is where meaningful worldview analysis begins.

The caller began by explaining his view of how sense perception works. According to him, our senses passively receive information from external objects through a causal process. As he put it:

Atheist: “You have the senses receiving the object. At one point at T1 the senses aren’t receiving anything, and then at T2 they are receiving the object. So there’s a causal relation where the sensible objects cause the senses to actuate.”

In simpler terms, objects in the world act on our senses, and that is how we come to know things. On the surface, this sounds fairly common-sense, and many Christians would agree with aspects of it. However, what often goes unnoticed are the assumptions already built into this explanation—assumptions about causation, the reliability of the senses, the orderly flow of time, and the mind’s ability to correspond to reality.

To reinforce his account, the caller appealed to what he called the principle of proportionate causality. He explained:

Atheist: “There’s a proportional relation between causes and effects… whatever is contained in the senses is like what the object is about.”

The idea here is that effects reflect their causes, and our perceptions reflect the objects we perceive. Again, this may sound reasonable. But in apologetics, the key question is not whether something sounds plausible, but why we should believe it is true—and whether a person’s worldview can actually account for it.

At that point, I began pressing the foundational issue. Rather than challenging the details of his theory of perception, I asked a question designed to expose what his view ultimately rests on:

Eli: “Would you say that you have to rely on your senses to demonstrate your senses?”

The caller answered plainly:

Atheist: “Yeah, of course. Yes.”

That answer immediately raises a problem. If we use our senses to prove that our senses are reliable, aren’t we reasoning in a circle? So I followed up:

Eli: “And is that not viciously circular?”

The caller responded by trying to defuse the concern. He argued that this kind of circularity isn’t a problem because it is the use of a rule rather than a premise:

Atheist: “It’s using rule circularity, not premise circularity… that’s a benign circularity.”

In other words, he claimed that trusting the senses to justify the senses is an acceptable kind of circular reasoning. But simply calling a circular argument “benign” does not explain why it should be trusted. So I pressed further and asked the question that really matters:

Eli: “What non-circular argument can you offer to justify the rule?”

At this point, the caller shifted away from the senses altogether and appealed to a deeper foundation. According to him, all justification ultimately stops with logic:

Atheist: “Obviously I think that it all, at the end of the day, terminates in the laws of logic.”

That statement is crucial. He was saying that logic is the ultimate stopping point—the place where explanation ends. But once that claim is made, logic itself becomes the subject of inquiry. So I asked:

Eli: “What justifies the laws of logic in your own worldview?”

His response was telling:

Atheist: “I don’t think that the laws of logic are the types of things to be justified… I think they’re axiomatic.”

In other words, logic is simply assumed. It does not need to be grounded in anything else. But this creates an obvious tension. Skeptics often object when Christians treat God as a foundational starting point. Yet here, logic itself is being treated as an unquestionable foundation. So I pointed this out directly:

Eli: “If I reversed that on you, you wouldn’t accept that. If I said God is axiomatic—that’s it—that would destroy argumentation.”

The issue isn’t whether people have starting points—everyone does. The issue is whether those starting points can be accounted for within a worldview, and whether the standards being applied are consistent.

The caller then tried to strengthen his position by claiming that the laws of logic are analytically true—true by definition, or “trivially” true:

Atheist: “I think they’re analytically true… trivially true.”

But this response only pushes the problem back a step. Appealing to analytic truth already presupposes logic, intelligibility, and rational necessity. So I responded accordingly:

Eli: “Appealing to triviality already presupposes intelligibility and logic. Those are the things I’m asking you to justify.”

As the conversation continued, the problem became even clearer when we discussed the nature of logic itself. I asked whether the laws of logic are descriptive or prescriptive:

Eli: “Are the laws of logic descriptive or prescriptive?”

The caller answered:

Atheist: “They’re descriptive.”

I then followed up with another key question:

Eli: “Are they universal?”

Atheist: “Yes.”

That combination is deeply problematic. Description alone—simply observing how things seem to behave—cannot give you universal, exceptionless laws that apply everywhere and always. You cannot move from “this is how things appear” to “this must be the case in all possible circumstances” without smuggling in something stronger than observation.

When pressed on how universality follows from mere description, the caller responded by denying the distinction altogether, claiming that everything is normative simply because it exists. But redefining terms does not solve the problem. It avoids it.

The same pattern reappeared when the discussion turned to induction and the uniformity of nature. The caller suggested that we assume induction in order to use induction. But that is not a justification—it is an admission that the worldview lacks one.

Throughout the exchange, a consistent pattern emerged. The atheist was freely using logic, induction, causation, and intelligibility, while being unable to account for them within his worldview. At the same time, he objected when God was presented as the foundation that makes those things meaningful.

This is precisely why presuppositional apologetics, as articulated by Cornelius Van Til and Greg Bahnsen, insists on pressing foundational questions. The Christian is not avoiding justification. Rather, the Christian is pointing out that only the Christian worldview can account for the very tools everyone uses to think, argue, and reason.

The takeaway is simple but important: if a worldview cannot justify the tools it uses to argue against God—logic, reason, and knowledge itself—then the problem is not that Christianity lacks evidence. The problem is that unbelief lacks a foundation.

That is what this exchange was meant to expose.

Note: This was created by Chatgpt based upon the transcript of my actual interaction on my recent livestream.

My interaction with the skeptic begins as the 1 hour mark. The link to the full livestream is here: https://www.youtube.com/live/-DhCeiOJ2p0?si=-xwJyqMyOSRITMeP

Glossary of Key Terms

Analytic Truth - A statement that is true by definition, where the meaning of the words makes the statement true (for example, “All bachelors are unmarried”). In the article, the issue is not whether analytic truths exist, but whether appealing to them can explain why logic itself is universally true and binding.

Axiom - A starting point or foundational assumption that a system of thought begins with. Everyone has axioms. The debate in the article concerns whether certain axioms (like logic or induction) can be justified within a worldview, or whether they are simply assumed without explanation.

Benign Circularity - A type of circular reasoning that some philosophers claim is acceptable, where a rule is used to justify itself (for example, using the senses to show that the senses are reliable). The article questions whether calling such circularity “benign” actually solves the problem of justification.

Causation (Cause and Effect) - The idea that one thing brings about another (for example, a fire causing heat). In the discussion, causation is assumed as real and intelligible, which raises the question of how such a principle is grounded within a non-Christian worldview.

Descriptive (Laws of Logic) - To say logic is descriptive means it merely describes how reality happens to behave, rather than prescribing how we ought to think. The article challenges whether purely descriptive laws can be universal and binding.

Epistemic Circularity - Circular reasoning that occurs when the thing being justified is also being assumed in the justification (for example, trusting logic in order to prove logic). The question is whether this kind of reasoning can genuinely provide knowledge.

Foundation / Foundational Beliefs - The basic beliefs a worldview rests on and does not derive from other beliefs. These include things like logic, reason, and the reliability of the senses. The article argues that foundations must be accounted for, not merely assumed.

Induction - Reasoning from past experience to future expectations (for example, expecting the sun to rise tomorrow because it has always risen before). The problem of induction asks why we are justified in assuming the future will resemble the past.

Intelligibility - The idea that reality can be understood, reasoned about, and meaningfully described. The article argues that intelligibility itself requires a worldview that can account for rational order.

Justification - A good reason for believing something is true. In epistemology, belief alone is not enough—beliefs must be justified. The central issue in the article is whether the skeptic can justify the beliefs he relies on.

Laws of Logic - Basic principles of reasoning, such as the law of non-contradiction (something cannot be true and false at the same time in the same sense). The article examines whether these laws can be grounded within an atheistic worldview.

Normativity - The idea that certain rules or standards ought to be followed. Logic is normative because it tells us how we should reason, not merely how we do reason. The article challenges attempts to reduce logic to mere description.

Prescriptive (Laws of Logic) - To say logic is prescriptive means it gives rules that govern correct reasoning. The article argues that universality and obligation make more sense if logic is prescriptive rather than merely descriptive.

Principle of Proportionate Causality - The idea that effects must be proportionate to their causes, and that something cannot come from nothing. In the discussion, this principle is assumed but not justified within the skeptic’s worldview.

Reliability of the Senses - The belief that our senses generally provide accurate information about the external world. The article explores whether appealing to the senses to prove their own reliability results in problematic circular reasoning.

Rule Circularity - A form of circular reasoning where a rule is used to justify itself (for example, using logic to defend logic). The article questions whether this actually explains why the rule should be trusted.

Transcendental Argument - An argument that asks what must be true for something else to be possible. In Christian apologetics, it asks what must be true for knowledge, logic, and reasoning to make sense—and argues that God is the necessary precondition.

Uniformity of Nature - The assumption that the laws of nature operate consistently over time. This assumption is necessary for science and everyday reasoning, but the article raises the question of how it is justified without God.

Worldview - A comprehensive framework of beliefs about reality, knowledge, morality, and meaning. The article shows that disagreements are not merely about individual beliefs, but about entire worldviews and their foundations.