#212 Atheist vs. Christian Debate Ends When This Question Gets Asked | Presuppositional Apologetics

Summary

---

Worldview Legacy | The Think Institute

Episode #212: Atheist vs. Christian Debate Ends When This Question Gets Asked | Presuppositional Apologetics

Air Date: June 16, 2026
Host: Joel Settecase, joined by co-host Alex
Guest: Brent (atheist, secular humanist, physicalist)

---

Episode Overview

This episode features a live exchange between Joel Settecase (Christian apologist) and Brent, a self-proclaimed secular humanist and physicalist atheist, focusing on the foundations of knowledge (epistemology) and the limits of certainty within competing worldviews. The main theme explores whether an atheistic, physicalist worldview can provide a sufficient basis for knowledge, or whether, as presuppositional apologetics asserts, such knowledge requires the existence of God.

---

Key Discussion Points & Insights

1. Setting the Stage: Worldview Positions

• Brent identifies as a secular humanist, atheist, and physicalist but focuses the conversation on the physicalist vs. presuppositional Christian apologetics debate.

  “For the purposes of this conversation, it’s the positive claim that no definition of God is self-consistent. I also add...that it may also be untestable.” (00:27, Brent)

2. Defining Knowledge: Gradients vs. Certainty

• Joel (using presuppositional apologetics) asserts that, under physicalism, true knowledge is impossible:

  “As a physicalist, I don't think that you can, properly speaking, understand anything. I don't think knowledge is possible to you as a physicalist.” (01:41, Joel)

• Brent rejects the classical “justified true belief” definition of knowledge and instead adopts a confidence threshold approach:

  “I think knowledge is just a gradient of belief...You believe something when it's a certain percentage, whereas you know something when it's a higher percentage.” (03:11, Brent)

Timestamp: 03:04–05:55

• They debate whether the threshold for knowledge should be fixed or context-dependent and whether this introduces arbitrariness into Brent’s epistemology.

3. The Problem of Infinite Regress

• Joel presses Brent on how he justifies his confidence levels and whether one can ever be certain even of their own certainty, introducing the philosophical problem of “infinite regress.”

  “As you are looking inwardly at Brent’s own confidence level...is that also dependent on a particular degree of confidence?” (07:54, Joel)
  “Your problem then is infinite regress. Even looking internally...you actually can't know anything to any degree of certainty whatsoever because you never have a starting point of certainty.” (08:44, Joel)

Notable exchange: (08:44–10:49)

• Brent admits he can’t have 100% certainty but insists that partial certainty is possible.
• Joel argues that lacking any ultimate ground of certainty, Brent’s approach collapses into arbitrariness or incoherence.

4. The Certainty Challenge: A Key Presuppositional Move

• Joel: “Are you certain that you can never have 100% certainty?” (11:40, Joel)

• Brent: “That really doesn’t make sense. Do you understand the question you’re asking? You’re asking if 100 can equal not-100. That’s a really bad question, Joel.” (11:45, Brent)

• The exchange becomes tense as Joel attempts to expose, by recursion, what he sees as a contradiction in Brent’s worldview: that asserting certainty about uncertainty is self-refuting.

Memorable Moment (12:09–13:41)

• Joel (pushing): “Are you certain that you can never be certain?”
• Brent tries to clarify but Joel insists the contradiction is inherent.

5. Breakdown & Impasse

• Brent attempts to clarify that he is not dealing in absolute binaries; Joel maintains that the lack of absolute certainty makes knowledge impossible on Brent’s terms.
• Brent accuses Joel of “building in a contradiction,” and that presuppositionalists “want to use words to supplant actual reasoning.” (14:28, Brent)

6. Presuppositionalist Analysis

• Joel (and Alex) give a post-dialogue analysis:

  “If you don’t start with a position of certainty, then you’re left with an...arm—I’m sorry, I’m not trying to smile, it’s...serious matter. You are left with a position of radical uncertainty about everything. You can’t even know that you can’t know things. And to say that I’m certain that I can’t be certain is very obviously incoherent.” (16:44, Joel)

• Alex echoes that denying any certainty is itself a universal claim and so self-defeating:

  “But if you say can you be certain? ...The first question is are you certain about anything? And they say no, that word anything is universal. So...it undermines their worldview.” (17:40, Alex)

John Frame Reference

• Joel summarizes John Frame's analysis: “[The atheist] is left in both radical irrationalism and radical rationalism...Rationalism because I’m going to claim to use my reason to make an all-encompassing claim about reality. Irrationalism because...I don’t have certainty, and so I actually have no epistemic right to make a claim about anything, let alone everything.” (18:50, Joel)

---

Notable Quotes & Moments

• Joel, on the necessity of certainty (09:26):

  “Without a platform of certainty, you can't ever get to the second subsequent belief...You need a starting point of certainty.”

• Brent, admitting limits (13:00):

  “Let me grant that I am certain about I can’t be uncertain. Explain the problem.”

• Joel, on contradictions (13:00):

  “You said you can’t be certain. I’m asking you if you’re certain of that. Your answer should be no, right?”

• Brent, pushing back (14:28):

  “You keep doing this thing where you assume 100% certainty, and so you’re building in a contradiction, which is why I keep rejecting the premise...It’s a really dishonest thing to do, Joel.”

• Post-dialogue analysis (16:44, Joel):

  “If you don’t start with a position of certainty, then you’re left with...radical uncertainty about everything...to say that I’m certain that I can’t be certain is very obviously incoherent.”

---

Timestamps for Important Segments

• [00:27] Brent states his worldview and the claim at issue.
• [01:41] Joel claims physicalists/atheists cannot have knowledge.
• [03:11–05:55] Exchange over the meaning of “knowledge” and confidence thresholds.
• [07:54–08:44] Joel introduces the infinite regress problem.
• [08:44–10:49] Discussion on infinite regress, certainty, and possibility of knowledge.
• [11:40–13:41] The “certainty about certainty” challenge; the core presuppositional apologetics move.
• [14:28–15:08] Brent’s accusation of category error/word games.
• [16:44–18:50] Joel and Alex’s analysis, John Frame reference, summary of implications.

---

Episode Summary

This rigorous debate exemplifies the presuppositional apologetics approach, where the Christian apologist repeatedly challenges the atheist to ground certainty, knowledge, and rationality without presupposing God. Throughout, the core question—“Are you certain that you can’t be certain?”—serves as the pivot, exposing (from the hosts' perspective) a fundamental incoherence in atheistic epistemology.

The exchange is lively, at times confrontational, and ultimately ends with both parties holding their ground but not bridging the philosophical divide. Joel and Alex assert that only a theistic worldview offers the necessary preconditions for knowledge, while Brent holds to a fallibilist, confidence-based epistemology that, according to the hosts, collapses under the weight of infinite regress and self-contradiction.

---

This episode is essential listening for anyone interested in epistemology, apologetic method, or the foundational disagreements between naturalism and Christian theism.

Transcript

[A]

All right, so next up we have someone. If it's who I think it is, we'll see here. This is Brent A. Hello.

[B]

Hello. Do you hear me?

[C]

We gotcha, Brent A.

[A]

Nice to meet you.

[B]

No, it's. It's bubble. Be me. Yeah, so good to meet you too. It's Joel and Alex, right?

[C]

That's right, correct. What's your world?

[B]

Oh, my worldview is secular humanist, atheist. I prefer the term ichthyist, but it really doesn't matter. For the purposes of this conversation, it's the positive claim that no definition of God is self consistent. I also add on, and this may be a cop out. I also add on that it may also be untestable. I was really just calling in to discuss pre supposition. I'm sorry, presuppositional apologetics. I encountered someone the other day and really could not find a connection point.

[D]

Now, if you like this episode and

[C]

you want to take your learning further,

[D]

you need to know about what we're doing to help revolutionize the way that Christian men interact with their faith. We want to help you get more equipped to lead your family to answer any objection to share and defend your faith.

[C]

And, and I'll tell you more about

[D]

what we're doing to help you do exactly that after the episode.

[C]

Stay tuned.

[B]

So maybe the question is about how do I understand from the position of a physicalist what your presuppositional apologetics of God entail?

[C]

How do you understand? Well, as a physicalist, I don't think that you can, properly speaking understand anything. I don't think knowledge is possible. To you as a physicalist.

[B]

I'm sorry, can you understand. I'm sorry, can you explain a little bit more about what you mean, that because I'm a physicalist, therefore knowledge is not possible?

[C]

Well, not. Let me say this again. You do know things, but your knowing things is inconsistent with your physicalism and your secular humanist atheist igtheism. And the reason for that.

[B]

I'm sorry, just real quick, I want to. Can we just leave the ichthyism and the other stuff just by the side and just do the physicalism versus the presuppositional apologetics? That's really what I'm trying to understand.

[C]

I don't.

[B]

Okay, okay, please go ahead then.

[C]

Okay. The reason why is because this isn't like a trap or anything like that, but worldviews are all the different components of a worldview all work together. And so you know, the fact that, you know that you're a physicalist and the fact that you're an atheist. Those are related. I don't know exactly how they'll come out in our conversation, but they are related. And, you know, not all atheists are physicalists. You could be an atheist idealist or whatever, an atheistic Platonist or something. But. So the reason why knowledge, why I say knowledge is not possible, given your system, is because, well, even.

[D]

Even

[C]

what is knowledge? How do you define knowledge? Would you agree that knowledge is justified true belief?

[B]

No, I think knowledge is more along the lines of high confidence in a given claim. So I would say that knowledge is just a gradient of belief. So you believe something when it's a certain percentage, whereas you know something when it's a higher percentage. And that higher threshold is what determines knowledge. I can't put a number to it, obviously, but that's how I view it.

[C]

You can't put it.

[B]

So it's not. No, because it depends on the claim. Right. If your claim is. Sorry, what?

[C]

I would think that if the claim is harder to prove, that would just be harder to get a higher percentage of certainty. But certain, certainly there must be a threshold when you know you have knowledge, right?

[B]

Yeah, but again, it would depend on the claim. I think we're looking at this from two different perspectives. So help me understand what I'm saying wrong about this, because to me, I would say I have a say. You claim that you had a dog that was your pet. I could have a 20 certainty that that is true, and I would just grant it because it doesn't seem particularly extraordinary. If you say I have an invisible. If you say I have an invisible dragon in my garage, then I would need to be like 95% certain that you were true. So maybe you can correct me on. No, I'm just saying I'm asking. Maybe you can correct me on my misunderstanding of what you were saying about the level of confidence. Because you seem to be saying. Yeah, so you seem to be saying that the level of confidence of 20% might. Sure. Thanks.

[C]

Okay. So it would seem to me like if knowledge is simply getting to a certain level of certainty, then that level of certainty is going to count as knowledge, no matter what you might say. I don't care as much if you have a dog or not, but certainly you wouldn't know it until you cross that threshold. And to have an equal standard is very important. Otherwise, you know, you're just inconsistent. It's totally. The whole system becomes totally arbitrary. If you say, well, depending on how I feel about a particular claim, I'll drop the threshold down or raise it up. I mean, then you're just completely arbitrary in terms of how you're defining knowledge in the first place. And you can't really say you have anything called knowledge. You can just say, I feel a certain way about a claim. But if instead you abandon that and you say, well, knowledge, I have to have 95% certainty. The claim about the dog and the dragon, the difference there is still going to be it. The standard remains the same, but then it's just harder to get to the certainty that is required for it to be knowledge given the dragon. Does that make sense? I want to move on to something else, but does that make sense? It's just harder to reach that threshold that seems to be more like what you're going for. Is that not true?

[B]

No. I think that we've kind of met somewhere in the middle and we can agree that the, the threshold may change or the metric may change. Either way. If you want to set like a given threshold and say, I have to know something greater than 80% confidence, then I would just say that the metric changes based on that depending on the claim. So I totally get where you're coming from, though. Yeah, you. You would need to, so to say, set a number in the view that you have. That makes sense.

[C]

So what is the unit that you are using to measure your confidence with? What is that unit?

[B]

A percentage.

[C]

Percent. Like, okay, so what is. What is being filled up when you get to 100%? What is that?

[B]

So 100% confidence would be. There is nothing that can possibly step me away from that belief.

[C]

Okay, so how, according to what means or what standard are you judging your certainty? How do you know if you have a certain level of certainty?

[B]

Observation of the natural world. I rely pretty heavily on science for that. Depends on the claims specifically. But generally for any existential claim, I want something scientific.

[C]

Okay, so hear, hear me. That's not exactly what I'm asking. I'm asking, as you are evaluating your own confidence level, do you have 100% certainty that you have a particular confidence level?

[B]

No, I have. There's no way to have 100% confidence.

[C]

Wow. Okay, so you have. So how do you evaluate your confidence level?

[B]

Use my perceptions. I use what the scientific journals publish as far as what exists and what does not exist. Again, I want to keep bringing it back to this existence idea because that's the question about God.

[C]

My, my question is, as you are looking inwardly and you're saying, what level of confidence does Brent personally have? And you go, I have a, a 20 confidence level, to use your example, that. That Joel has a dog. Okay, I've got 20. As you are looking inwardly at Brent's own confidence level, is that also dependent on a particular degree of confidence? Like I'm. I'm 25. Sure that I'm.

[B]

Yes, absolutely. Yep. Absolutely. It already. It already includes that.

[C]

Okay.

[B]

It already includes that. Yeah, it would. It would include. It would include the fact that I. I consider what the claim is. I consider what a general type claim is. I consider my. My own fallibility and my perceptions and how much I trust people and how much I don't. Yes, that's. That's all rolled into that. Yeah.

[C]

So your problem then is infinite regress. Even looking internally.

[D]

Yeah.

[C]

So you actually can't. You actually can't know anything to any degree of certainty whatsoever because you never have a story that's not true.

[B]

No, no, I. No, I can't. I can't. I can't. No, I can't.

[C]

What was I gonna say? What was I gonna say?

[B]

I can't know anything to a hundred percent certainty.

[C]

What was I.

[B]

Not that I can't know it to any percent certainty.

[C]

Brent, you cut me off. I assume that means you know what I was gonna say. What was I gonna say?

[B]

No, no, I cut you off because you misunderstood what it is that I said. What I'm saying is I can't have a hundred percent certainty. But. But that doesn't naturally follow that I can't have any certainty.

[C]

Brent, you have what's called the problem of the infinite regress. And it's. It's. It's actually internal to your own. Even your own examination of your own confidence level, because you don't have a starting point of certainty. In your own view. There's. Think of it as a bottomless hole. You've got no place to stand by which you can even begin to evaluate your. Even your own level of confidence in a claim, let alone how confident you are in a claim. So you can't even get to the point because you're starting from an infinite regress. You can't actually ever get. You have an infinite chasm to cross before you can ever get to. I have this level of confidence that Joel has a dog. You can't ever actually get there because you're never sure at all that you're even confident at all, that you are confident at all, that you are confident at all, that you are confident of that claim. It's the problem of the infinite regress. How do you know? A, because of B. How do you know B because of C? How do you know C? If there's never anything certain at the beginning of that chain of argumentation of logical inference, then you can't ever get to your destination because logically you're going infinitely back into the past. And, and respectfully, that's exactly what I'm hearing from you. You're saying I have different.

[B]

Yeah.

[C]

No, arbitrary.

[B]

Absolutely. Can I just summarize? Can I summarize what I heard so far? Let me try to steal, man, real quick. Yeah, awesome. So you're saying that because I can't have a hundred percent certainty, then everything relies on something else. There is some necessary criteria by which I judge the next thing in order to make sure that I convinced of the end thing. Right. Do I have that correct so far?

[C]

I'm saying that without a platform of certainty, you can't ever get to the second subsequent belief. You need a starting point of certainty. And because you don't have that according to your own view, I think you actually do have that. By the way. I mean, we can prove this very quickly. I mean, are you certain that you can never have 100% certainty?

[B]

That really doesn't make sense. Do you understand the question you're asking?

[C]

I understand.

[B]

You're asking if 100 can equal not 100. That. That's a really bad question, Joel.

[C]

So it should be very simple to answer. Are you certain?

[B]

No, it's not simple to answer. You're including, you're including a paradox in the question. I can't answer that. Objective terms of the question.

[C]

So, so you made a claim. You said I can never have 100 certainty. Do you remember making that claim?

[B]

Yeah.

[C]

Do you stand by it?

[B]

Of course.

[C]

Are you certain that you stand by it?

[B]

Of course.

[C]

Okay, I rest my case.

[B]

No, you don't rest your case because you're, you're really just building in a contradiction in the question as you ask it. Do you understand that maybe this is the disconnect between me and the presuppositionalists?

[C]

Yeah, maybe that's what I'm Explain. Explain how there's not actually a contradiction in it. I'm building one in. So explain how your view is not contradictory. Go ahead.

[B]

No, you're building in the contradiction you're asking, is it possible to be 100 certain about being 100 certain? Right.

[C]

The. The, the answer, according to your view, is no.

[B]

No, no, no. That's. I, I want to clarify the question, Joel. I don't want to move on. I want to clarify the question. You're asking, Is it? You're asking. You're asking, is it 100 certain that I'm 100 certain about being 100 certain, right?

[C]

No, no, listen. Listen to me very carefully.

[B]

You said that was really rude. That was really rude. Jewel, I'll listen, but you really need to know it's not okay, right?

[C]

Listen very carefully. Are you certain that you can never be certain? Are you certain about that?

[B]

Am I certain about being certain or am I uncertain about being uncertain?

[C]

Is this really happening, Brent? Yes, this is why I said listen. Because carefully.

[B]

Yeah, because this is the.

[C]

You made a claim that you can never have certainty, objective, absolute certainty. You made that claim. I'm asking you if you are certain you can never be certain.

[B]

Joel, let's play. Joel, I know you like Jay Dyer. Your answer, all the possibilities. Number one, Let me grant. Let me grant. Let me. Me grant that I am certain about I can't be uncertain. Explain the problem.

[C]

No, no. You didn't say you can't be uncertain. You said you can't be certain. I'm. Do you remember what you said, Brent? You said you can't be certain. I'm asking you if you're certain of that. Your answer should be no, right? So is your answer no,

[B]

sure? Let's go with that.

[C]

Okay, so you're not certain that you can't be certain. So you want to take back that claim then?

[B]

No, I am not certain that I can't. You keep doing this thing where you assume 100 certainty, and so you're building in a contradiction, which is why I keep rejecting the premise of the question you're asking. Can I be 100 certain that I can't be 100 certain? It's a really dishonest thing to do, Joel. I want to get back to what my disconnect is. I want to get back to what my disconnect is from the presuppositionalist. I know you, and now I think I know what it is, is that you want to use words to supplant actual reasoning.

[C]

Brent, actual reasoning involves uncovering contradictions and revoking them and renouncing them.

[B]

Now, the contradictions don't exist without your God existing, right?

[C]

You've told me that you can't be certain.

[B]

Contradictions don't exist without your God existing, right?

[C]

You said, yes, I'm certain.

[B]

So that contradictions don't exist without your God existing, right?

[C]

Listen to me, do you.

[B]

Contradictions don't exist without your God existing, right? Listen, contradictions don't exist without your God existing.

[A]

If you're just going to repeat the same question over and over again, you are going to get muted.

[C]

Ladies and gentlemen, this is where atheism leads. This is where it leads. And it's not just atheism, it's other non Christian worldviews too. Last week we had two people who ended their debate simply repeating the same thing over and over. Now, Brent, you've been shown that there is a contradiction in your worldview. You're certain that you can't be certain, so you can say, well, you don't understand. You know, there's degrees of certainty and whatnot. I've already explained to you the problem of the infinite regress. Your problem of the infinite regress. This is why knowledge is not possible without God. Because without God to give you absolute certainty of, of a, of your epistemological starting point, you can't know anything at all. You can't even know that you're not certain, but you are certain of that. This is a contradiction. Your worldview leads necessarily to a contradiction.

[A]

I'm going to unmute you now. We are out of time. I'll give you a 30 second ending statement if you'd like to address what Joel said, but please address it. And you got 30 seconds. Thank you.

[B]

No, I'm good, thank you. It led me to understand better how I'm not making the connection between presuppositionalists and myself. So I have nothing more to add. I appreciate you bringing me up.

[C]

Good.

[A]

Have a good night.

[C]

Thanks for coming on. Yeah, just quick 30 second analysis. That is where fallibilism leads. We didn't get into the term fallibilism, but Alex, of course you and I have talked about fallibilism quite a bit. You've actually taught me a few things about fallibilism and I like to think that I taught you a few things along the way as well. But no, in all seriousness, if you don't start with a position of certainty, then you're left with an arm. I'm sorry, I'm not, I'm not trying to smile. It's. This is a serious matter. You are left with a position of radical uncertainty about everything. You, you, you can't even know that. You can't know things. And to say that I'm certain, that I can't be certain is very obviously incoherent. What would you, what would you say? Triple X. What would you say if he said no? No, I'm. Well, I'm not certain. Yeah, what if he said I'm said

[A]

no, they think it's a clever. I mean, respectfully, he didn't even know to do that. Right, but the fallibilists think that's a clever thing to say.

[C]

Yeah, no, I'm not.

[A]

Yeah, yeah. But if you say can you be certain? And they say, or if you. The first question is are you certain about anything? And they say no, that word anything is universal. So the second they say no, I'm not certain about anything, they're making a universal claim just in their answer. It undermines their worldview.

[C]

Explain why.

[A]

Because even if they say no, I'm not certain that I'm not like they don't even get there.

[C]

Right, right.

[A]

They can't even get to that second question. It's already making a universal statement.

[C]

It's actually a claim of certainty that there is not one thing in the all of existence about which I am certain.

[D]

Yeah, right, that's.

[A]

It ends there.

[C]

Yes, you're right, that's actually. That's a great point. You're right, it's a. The way I like to frame it is the way that John Frame does it. John Frame is the most perfectly named person by the way frame.

[D]

He frames.

[C]

He's just got a perfect framework for everything. But he talks about how the. The atheist is left in both radical irrationalism and radical rationalism. Rationalism because I'm going to claim to use my reason to make an all encompassing claim about reality. Irrationalism because I recognize that my brain is contingent, I don't have certainty, and so I actually have no epistemic right to make a claim about anything, let alone everything. So radical irrationality and rad rationality and yes, it is just as absurd as saying I'm certain that I can't be certain about anything. He thought I was baking in a contradiction. I wasn't. I wasn't building or building a contradiction. I was literally asking him, are you certain about that? And the reason why it was so infuriating is because it actually doesn't make sense. But I didn't build that into it. I was just using his own worldview

[D]

against itself, against it.

[C]

So.

[A]

Yep, exactly.

[D]

You're a Christian man, you want to build a legacy, answer the world's questions and lay down a solid foundation for your family in God's word. But everywhere you look you see decline, disorder, chaos, your neighbors don't know the Lord and too many churches are filled with apathy. In today's world, we need men who, who understand theology, know scripture and who are committed to leading their families in the Biblical worldview. That is why we're building the Hammer and Anvil Society, the ultimate discipleship community for Christian men. With weekly cohort calls, a full library of resources and courses, weekly challenges and live teaching. You're going to sharpen your mind and your character. Our full library of courses is going to help you deepen your knowledge in the Christian worldview, family, discipleship and apologetics the defense of your faith. But it's not just about building your knowledge base. As important as that is, it's also about brotherhood. That's why you'll also have access to an online community and live cohort calls, live teaching and real accountability so you can have fellowship with like minded brothers who are on the same journey as you. Member Kevin says the Hammer and Anvil Society has been the most beneficial thing for my family's spiritual growth in years. This unique brotherhood has made me more bold in my witness and more sensitive to God's leading. AJ says today I stand stronger and more rooted in my faith. The Hammer and Anvil Society has been instrumental in transforming me into the man of God I am striving to be. Get unlimited access as a member or try out a single course in the

[C]

subject of your choice.

[D]

Learn more now. Go to thethink.instute society. Get equipped. Build your legacy in community.

[C]

Join today.