Debating an Atheist

Updated: Sep 16, 2019

We've written an article responding to objections we received from atheists over the content of this article. Read more here.

I recently got into a debate with a group of atheists on the popular social media site called Reddit. As you would expect, I pressed them on the topic of truth (Or objective truth, absolute truth). Their initial responses were quite consistent since I did not explicitly reveal that I am a Christian in my initial question. Once it became apparent that I am a Christian, the tone changed a lot and from there it went downhill. We are a presuppositional apologetics ministry, however, I fully understand the following quote from classical apologist William Lane Crag responding to comments on his recent NYT interview:

I think that the intellectual veneer of contemporary atheism is finally beginning to wear thin. The sort of negative comments to my NYT interview would once have appeared very intimidating to most Christians. But today Christians seem to recognise their posturing and empty bravado for what it is. It's really atheism that is very anti-intellectual in our culture. A couple of years ago someone aptly compared it to a little pussycat who gets his back up and puffs up his fur trying his best to look menacing. That realisation is real progress culturally speaking. The comments to the interview do make it alarmingly clear that we've really got our work cut out for us in winning our culture, but at least the church is no longer so cowered and afraid.

Now the subreddit on which the debate occurred is called r/DebateAnAtheist and I have been a visitor there a few times. I asked the simple question of whether there exists something such as objective truth and whether we can obtain it. The responses at first were surprisingly consistent and unexpected:

Yes, and yes, but we can never be absolutely certain we have.
Objective truth exists, but we have no way to obtain it.

You can easily guess my followup questions on these statements. The claim that we cannot obtain any absolute truth is inherently absurd because it in itself is an absolute truth claim and hence is self-refuting. If the atheist also claims not to be absolutely certain that absolute truth doesn't exist, the absurdity is only pushed back one level. Is the atheist absolutely certain that they aren't absolutely sure that absolute truth exists?

I was quick to point this out to the group of atheists and from there, things turned South very quickly. The atheist that claims that he cannot know anything for certain not only embraces an absurdity, but has also completely given up knowledge. See, the issue is that if you do not know anything for certain, you do not know anything at all. This derives another absurdity inherent in the atheist position as the atheist claims that there is no God by definition, yet the atheist also cannot know anything for certain. How can you claim God doesn’t exist and in the very next sentence claim that you cannot know anything?

The atheists also shockingly accepted this, stating that they have no solution BUT, neither do I apparently even though it is a non sensical claim, as you cannot concede that you don’t know anything, and in the next sentence claim that you know I don’t know anything at all as well — it’s wholly inconsistent. How did they come to the knowledge that I know nothing if they already conceded to knowing nothing? They can’t have it both ways.

For the new reader, it may be well to explain exactly why the atheists cannot consistently know anything, and how their worldview reduces to absurdity - as not all atheists readily accept that they cannot know anything in their worldview.

The Preconditions of Intelligibility

Now before we dive deeper into the discussion I had, it would be beneficial to talk about the preconditions of intelligibility: the preconditions of intelligibility are those things that are necessary (must be accepted as true) for us to begin to make sense of the world around us. For example, our ability to use logic, the reliability of memory, etc. For starters, to make sense of the question: “What are the Preconditions of Intelligibility” we’re assuming the Preconditions of Intelligibility: that our question makes sense, that it won't change 3 seconds after you read it, and that it will be understood by those you are asking the question to. When you say: "The sky is blue", you are assuming the Preconditions and making a truth claim. You're assuming that your reasoning faculties are telling you the truth about the world around you and that it is indeed objectively, absolutely true that the sky is blue. Other concepts that are included in the Preconditions of Intelligibility are:

  1. The reliability of memory

  2. Reliability of our senses

  3. Laws of logic

  4. Uniformity of nature

Any worldview must provide the foundation for these preconditions as they are inescapable in the world we live in. If the worldview fails to do so, the worldview will literally crumble in on itself - as the adherent must inescapably assume the preconditions without a foundation. See, if we really couldn’t ever know anything (if we had no foundation for the Preconditions), then we shouldn’t even be able to know that we don’t know anything as it would be something that we know. Further, it is not consistent with the way we experience reality. Take these atheists for examples, they claimed to not know anything yet in a different debate they will be spitting out facts left and right as if they DO know things. They’re not consistent.

Every worldview must provide a foundation for the Preconditions of Intelligibility. Since we’re talking about atheism in this article, let’s climb into our atheist shoes and see if we can find a foundation for these preconditions:


The Atheist materialist worldview (if you define it as a lack of belief in God or the belief that there is no God, it doesn’t matter) doesn’t have the Christian God at its foundation. So what or who is the ultimate authority of the atheist? The atheist himself, of course, as he or she is the arbiter of truth in their worldview. They might claim that science or scientific consensus is the authority, but there is no knowledge that they come to believe without first hearing it, reading it or listening to it themselves. In the end, they can’t escape interpreting the ideas in their own mind first before accepting it as truth, therefore they are their own ultimate foundation.

There are a few problems with a person being their own authority/foundation. Firstly, atheism is directly connected with materialism and hold to the theory of evolution and billions of years mutation and selection to explain their origin. How can the atheists trust their senses to be reliable and provide them with input consistent with objective reality if this is the case? See the issue with the atheist worldview and with them being their own foundation is that they have no way of knowing whether their senses are working and whether their reasoning is valid. Consider:

The theory of evolution as proposed by Darwin in its modern form states that traits that are most beneficial to reproduction/survival will be selected above other traits. What this entails, is that the consistent evolutionist must believe that our only goal and purpose is to propagate our DNA - not to discover truth or do science, etc. Our minds will wilfully deceive us if it gives us a reproductive advantage. There is no reason to trust in the thoughts and reasoning of such a being that came about in the manner described by evolutionists. Darwin himself acknowledged this problem, and it has been dubbed "Darwin's Doubt" in recent literature/

If a person only had invalid reasoning, how would they know that their reasoning is invalid? They would not be able to. You say they can look at other people’s reasoning and conclude that theirs are wrong, but that is using valid reasoning. If you are only reasoning invalidly, you wouldn’t know it if you are the ultimate authority - and this implies once again that you can be wrong about everything you claim to know, producing the absurdity discussed above.

Further, the atheist runs into the problem of solipsism. The atheist can think that he is in a room with blue walls when he is actually a brain in a vat in a room with orange walls - being fed input by a computer.

It is mainly due to the previous two points that Atheists readily concede that they cannot know objective truth, but this derives an absurdity, because the claim that you cannot know truth is, in fact, a truth claim - which means that they cannot know that that the cannot know anything to be true, which again is a truth claim, which they’re not supposed to know. See, if you truly cannot know anything, you shouldn’t have been able to figure out that you cannot know anything, as then you would know something. The atheist cannot escape the fact that they, in fact, DO know things for certain (funny right?), and this betrays that they are living in God’s world, with God as the foundation, but they do not honour Him as God (Romans 1), and instead try to be their own gods. The reliability of our senses are not found within ourselves but are rooted somewhere else.

To return to our four preconditions mentioned (there are more), we have seen that the atheist worldview fails to provide for the reliability of our senses and reasoning. Now, the consistent atheist will also need to believe that the laws of logic are social constructs and change over time - as there is no such thing as “an immaterial universal law of logic” in their worldview. Therefore, I would be fully in the right to claim, and they would agree if they are consistent, that according to MY logic, it is perfectly reasonable to assume that my car is at work in Johannesburg AND at home in Pretoria right now. Can that be the case? Of course not! You, I, and the atheist know this, but this is what their worldview can provide them. The laws of logic are rooted somewhere else and is certainly not a social construct.

The second to last one we’ll talk about is the reliability of memory and this links into the problem of induction that the atheist worldview also faces. How do you know that your memory is reliable without relying on your memory? For example, if you say I know my memory is reliable because it always has been in the past, you are appealing to your memory which is fallacious as you are assuming your memory is reliable to prove it is reliable. The reliability of our memory is rooted somewhere other than in ourselves.

And finally, the last one mentioned — the uniformity of nature. The atheist will run into what is called the problem of induction. On what basis does the atheist assume that the future will be like the past? This fact is at the core of the scientific enterprise, but the atheist has no reason to believe this simple fact. We expand more on it below:

The Problem of Induction

The problem of induction is formally defined as:

The problem of induction, the problem of justifying the inductive inference from the observed to the unobserved. It was given its classic formulation by the Scottish philosopher David Hume (1711–76), who noted that all such inferences rely, directly or indirectly, on the rationally unfounded premise that the future will resemble the past. There are two main variants of the problem; the first appeals to the uniformity observed in nature, while the second relies on the notion of cause and effect, or “necessary connection.

Check out this video by an internet atheist below, where he ironically mocks creationists while discussing the problem of induction.

Remember that the entire scientific enterprise is based on the principle of induction, therefore, if we have no reason or basis for the use of inductive reasoning, the entire scientific enterprise falls apart. Consider:

  1. I pick up my water bottle

  2. I let my grip loosen on the bottle

  3. The bottle falls on the ground.

I observed the above three steps. I now want to know whether step 3 will occur again should I repeat step 1 and step 2.

My prediction on this will be based on the experiment I conducted in the above three points. The problem? All those three points happened in the past. Let’s complete the experiment a second time, regardless:

  1. I pick up my water bottle

  2. I let my grip loosen on the bottle

  3. The bottle falls on the ground.

Amazingly the third step resulted again! But now I want to know whether step 3 will occur again should I repeat step 1 and step 2.

My prediction on this will be based on the experiment I conducted in the above three points. The problem? All those three points happened in the past. This time, however, I conducted the experiment two times already, so that could aid in my prediction. The problem? Both those experiments were in the past and I have no reason to assume that the future will be like the past.

The above structure should provide us with a good example of the devastating effect the problem of induction has if you do not have a solution. You can never be certain that the bottle will drop no matter how many times you complete the experiment. You might ask, “But the future has always been like the past?” — that may be so, but “the future has always been like the past” statement is itself an appeal to the past and does not solve the problem as it is circular. So where do we go from here? Are we stuck in a state of inescapable uncertainty? The problem of induction entails that the only thing we can be certain of in science (unless we have a solution for the problem) is that we can’t be certain about anything — the past experiments conducted amount to nothing!

The Solution

The consistent atheist cannot know anything for certain based on the foundation of their materialism. The admission that they can be wrong about everything they claim to know is absurd.

If the atheist could be wrong about everything he/she claims to know, they would not be able to know that they can’t know anything. Therefore the atheist cannot consistently open his/her mouth and make a statement without betraying their worldview. Atheists DO know things, and it is this fact that exposes their belief in God which they suppress. Supplementing this problem is the fact that people are not all-knowing. This means that everything we claim to know can be contradicted by something we don’t know yet.

Therefore, for us to know anything at all, we would need to be all-knowing OR have revelation from someone who does. God.

Only God knows everything, and unless we start with Him as our foundation our worldview will reduce to absurdity. The God of Scripture is also the only one who can provide us with the preconditions of intelligibility.

How Does God act as the Foundation for the Preconditions?

The Bible, being God’s Word, reveals to us the nature of our being and the world around us.

In the Creation account of Genesis 1, we come to the conclusion that God is a God of order and not of chaos. He created each and everything on a specific time with a specific goal in mind - nothing was left to chance. The wonder of this is because God is a God of order, we can also expect that His creation would be a creation of order and uniformity. God’s creation is not chaotic, rather everything works according to a set of rules which God has set in place.


The laws of nature are written by the hands of God in the language of mathematics

The reliability of memory and reliability of our senses

God reveals in His Word that we are created in His image, and we have been given the explicit command to develop and study His creation. This entails that we can trust in our senses and memory to enable us to do so, as they were also created by God.

Laws of logic

The laws of logic and correct thinking are universal and applicable to all humans because they are rooted in God. Thinking in a manner conforms to God’s thinking is logical and true.

Uniformity of nature

God reveals that He has created the universe in an orderly and understandable fashion and that He will continue to uphold His creation — which provides the foundation for the assumption that the creation will act the same way tomorrow as it does today and did yesterday.

This uniform and orderly creation we come to expect and do find is the foundation of all modern and historic scientific endeavours. Remember that science is dependent on the principle of induction: What happens in the past can be used to extrapolate what we can expect to happen in the future. The Christian worldview provides the foundation for this incredible precondition to doing science that many of us take for granted without ever really thinking much about it. In the atheistic worldview, there is no reason to expect an orderly universe and no way to prove that the future will be like the past without appealing to the past which results in a fallacious circular argument.

From the biggest star system to the smallest atom, everything was created by God and He conserves it all.

Could There be Multiple Solutions?

Only the Christian God can act as the foundation for the Preconditions of Intelligibility.

Firstly, as the Bible is clear that there is only one true God capable of providing for the Preconditions and secondly as it can be intellectually demonstrated that all world-views that do not have the Christian God as their foundation, will necessarily reduce to absurdity. This can also be expected from Scripture, as Scripture is clear that there is in essence only two worldviews, Christian and non-Christian.

If there were more than one solution, it would be possible for someone to stand before God with a valid excuse for their rebellion - but the Bible is clear that one has an excuse and apart from Christ all of us stand condemned.

Assuming the Preconditions as Properly Basic

In classical foundationalism, beliefs are held to be properly basic if they are either self-evident axioms or evident to the senses (empiricism).

A common counterpoint is that we do not need God as the foundation for the Preconditions, as they are properly basic beliefs. To show why we cannot take the preconditions as properly basic beliefs, we need to ask the question, why do we take some beliefs as properly basic, and not others?

Either we take on beliefs in:

  1. An arbitrary manner

  2. Because they are informed by something or someone

If the unbeliever appeals to A, then we can arbitrarily assume they are wrong, and our position would be just as valid. Arbitrariness is one of the deepest intellectual sins and doesn’t get us anywhere. If the belief is arbitrary, there is no guarantee that it is right, and the unbeliever still has the issue of possibly being wrong about everything he claims to know and hence has no real knowledge, which is absurd.

If the unbeliever appeals to B, he is using fallacious circular reasoning. The only way we are informed by something is through our senses and reasoning — so being informed by our senses and reasoning that our senses and reasoning works, is fatal.

Assuming the Preconditions on Impossibility of the Contrary

A different and interesting claim that I only recently encountered tries to use a transcendental approach the justifying the preconditions without using God as a foundation. The claim here is that we can assume the preconditions by the impossibility of the contrary. Therefore the unbeliever would claim that:

  • His reasoning works by the impossibility of the contrary

  • His senses work by the impossibility of the contrary

  • The laws of logic are established by the impossibility of the contrary

  • His memories are reliable by the impossibility of the contrary

  • Etc.

This is quite easy to refute. In the same order, the unbeliever must answer the questions:

  • Is it possible that your reasoning does not work correctly?

  • Is it possible that your senses do not function correctly?

  • As in the atheist worldview, there are no immaterial things, how exactly are the laws of logics established by the impossibility of the contrary if they can only be social constructs?

  • Are all your memories 100% accurate? If not, is it impossible that all of them are inaccurate?

The answer to all these questions will easily demonstrate that the atheist cannot, in fact, assume the preconditions by the impossibility of the contrary.

Ending The Debate

To demonstrate the absurdity of an unbeliever's worldview is only part of the apologetic process. Any apologist who destroys the idols of the unbeliever and also fails to point the unbeliever to the only place where there is lasting peace and salvation has accomplished nothing.

The proclamation of Jesus Christ as Lord and the Gospel is an essential part of the presuppositional apologetics methodology. The unbeliever can be invited to put himself on the Christian position in order to see that it provides the necessary grounds for intelligible experience and factual knowledge— thereby concluding that it alone is reasonable to hold and the very foundation for proving anything whatsoever.

People debating

The unbeliever must then be called to repent and put his/her faith in Jesus Christ and hence abandon their previous way of living.

So I tell you this, and insist on it in the Lord, that you must no longer live as the Gentiles do, in the futility of their thinking. They are darkened in their understanding and separated from the life of God because of the ignorance that is in them due to the hardening of their hearts. Having lost all sensitivity, they have given themselves over to sensuality so as to indulge in every kind of impurity, and they are full of greed. That, however, is not the way of life you learned when you heard about Christ and were taught in him in accordance with the truth that is in Jesus. You were taught, with regard to your former way of life, to put off your old self, which is being corrupted by its deceitful desires; to be made new in the attitude of your minds; and to put on the new self, created to be like God in true righteousness and holiness. Ephesians 4:17-24

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