Deconstructing C.S Lewis on Reasoning to Atheism

Over the past few months I’ve seen this quote bouncing around Facebook occasionally and picked it as the topic for my new blog article.

The quote can be found here: C.S Lewis on Reasoning to Atheism

“Supposing there was no intelligence behind the universe, no creative mind. In that case, nobody designed my brain for the purpose of thinking. It is merely that when the atoms inside my skull happen, for physical or chemical reasons, to arrange themselves in a certain way, this gives me, as a by-product, the sensation I call thought. But, if so, how can I trust my own thinking to be true? It’s like upsetting a milk jug and hoping that the way it splashes itself will give you a map of London. But if I can’t trust my own thinking, of course I can’t trust the arguments leading to Atheism, and therefore have no reason to be an Atheist, or anything else. Unless I believe in God, I cannot believe in thought: so I can never use thought to disbelieve in God.”

Each time I’ve read this, I’ve been completely baffled by the quote. On my mission I encountered some leaders who were really big C.S. Lewis fans, and even got a few quotes that I liked myself, but never have I encountered such a weird and circular quote.

So OK, here goes Mr Lewis:

“Supposing there was no intelligence behind the universe, no creative mind.”

OK, we are speaking hypothetically. We are supposing that the universe has no (I assume “creative”) intelligence behind it. We are pretending to be atheists for a moment while we consider an argument.

“In that case, nobody designed my brain for the purpose of thinking. It is merely that when the atoms inside my skull happen, for physical or chemical reasons, to arrange themselves in a certain way, this gives me, as a by-product, the sensation I call thought.”

That would be correct. We obtained a brain via millions of years of evolution which had no intelligence behind it. OK.

“But, if so, how can I trust my own thinking to be true?”

OK, just wait a second.

Where was the jump (from):

  1. A creative intelligence designing our brains (to)
  2. Us being able to trust that our own thinking is true


Embedded in this argument appears to be some kind of assumption. The assumption is that if a creative intelligence is behind the creation of our brains, then we can trust them to think “true thoughts”. How on earth does that work??

The reason I say that assumption is present, is because this is a “counterfactual” argument; saying that IF there were no creative intelligence THEN we couldn’t trust our thoughts to be true. The corollary is implied.

Whence the assumption that even with a creative intelligence behind it all we can trust our thinking to be true?? No matter who you are, no matter which human being on this planet, you think you are right about your worldview. By definition, that means everyone else varies from slightly wrong to very wrong (according to you). Hence YOU trusted your thoughts to be true, and so did they (everybody else), yet somebody is wrong (presumably everyone else).

Regardless of whether there is a creative intelligence behind our brains, we cannot trust our thoughts to be true “just like that”. Because so many people are thinking inaccurate thoughts.

“It’s like upsetting a milk jug and hoping that the way it splashes itself will give you a map of London.”

Another massive jump! Whence the jump from being able to or not being able to trust our thoughts to the Boeing 747 argument?

I presume this is some obscure reference to the theory of evolution. If it indeed is, then it’s obvious Mr Lewis completely misunderstands evolution.

“But if I can’t trust my own thinking, of course I can’t trust the arguments leading to Atheism, and therefore have no reason to be an Atheist, or anything else.

As mentioned above, regardless of whether there is a creative intelligence, you can’t trust your thinking to be true. This argument can be turned on its head as well (which could be inferred from the “or anything else” part) — in a universe without God, thoughts leading to theism would be inaccurate and “untrustworthy” too, we’d just never know! This could possibly be the reality we live in!

“Unless I believe in God, I cannot believe in thought: so I can never use thought to disbelieve in God.”

Another very strange jump — what exactly does it mean to “believe in thought”? (I presume it means believing that our thoughts are, or can be true). Why does God have to exist in order for our thoughts to be “true”?? I genuinely don’t see the connection. In any case I’m sure atheists “believe in thought” AKA they believe we are capable of knowing “the truth”.


This quote is really one of the weirdest and most circular arguments I’ve ever heard. I think essentially it goes like this:

  1. In a universe without God, our brains evolved just by chance (OK)
  2. Brains that evolved “just by chance” are super-duper unlikely. (This demonstrates a lack of understanding of how evolution works)
  3. Brains that evolved just by chance “can’t” be thinking truth — (??) We can’t trust them to think truth — (??)
  4. Because they can’t think truth, their thoughts and arguments about atheism can’t be true — (but then thoughts about theism can’t be true either?? In a universe without God there might still be theists!)
  5. Presto! There must be a creative intelligence then!

I still acknowledge the possibility that I just totally misunderstood the quote. Please, anyone, enlighten me.


  1. Pingback: Book Review: The Divine Reality: God, Islam & The Mirage of Atheism – Shawn's Odyssey

  2. Oladayo Onitayo

    What I’d try to do is to explain what I think Lewis is saying and then, possibly, you can be led to see where you probably misunderstood him. Here is my own thesis of his quote.

    1. The belief that there is no God is a product of a thought. As such, if we assume without necessarily conceding that this is actually true, it means that everything, including the thought that produced that belief, must have happened solely by chance.

    2. Progressing in his thought, Lewis is saying that for the sake of proving (1) above, we should identify an orderly or intelligent act such as the map of London. Since atheists believe that creation must have come into being by chance, it shouldn’t be out of possibility to produce London’s map by just “Upsetting a milk jug.”

    3. Unless you can prove otherwise, Lewis is insinuating that no one, atheists or theists, would put their money on this assertion 2 above. That is, even atheists won’t agree that by a simple random act such as upsetting a milk jug, London’s map can be produced. Stated differently, it means that the existence of orderliness or “thought” without a creative intelligence is impossible ab initio.

    4.Holding (3) above to be true, it means that the thought that produced the belief of atheism is an intelligent one which could only have existed in the first place because there is a calculated, determined, and intentional effort of someone (not by chance).

    5. As such, since atheism takes its root from intelligence and intelligence is not possible by chance, then the belief that there is no God can only be reasonable by accepting, even if for a moment, that there is an intentionality somewhere.

    6. Granted, brains that evolved by a creative power can think wrong. But the idea of the brain or thought evolving just by a product of chance or randomness is not even possible in the first place, remembering the fact that London’s map cannot be drawn by just upsetting a milk jug.

    7. Atheism can, therefore, be reasonable only when we, first of all, accept theism. It is only by acknowledging theism that Atheism can be sensible.

    1. shawn (Post author)


      Without writing a very lengthy response….

      I think the key here is whether intelligence could result from “chance”. Reality is that it can. When we were babies, we knew nothing, but continuous interaction with our environments helped our brains to build models and learn. Reality is that our evolution followed the same trend, on a much larger timescale.

      Yes, by chance, over millions of years of gradual evolution, eventually there arrived on the scene Homo Sapiens, and we have a neural network sophisticated enough to have this conversation on my blog after many years of learning. These networks (our brains) evolved and there’s no reason or need for them to have a grand creator.

      In any case, if you believe in (some version of your) God, you’ve not actually solved the philosophical problem — because God is then an intelligence that arrived “just by chance”. So GOD IS your metaphorical “milk jug” being upset and producing a map of London. Somehow, by chance, there’s this massive, grand intelligence that just happened to be intelligent and exist? We’ve outsourced the philosophical problem one level up, then invoked “we don’t understand the mysteries of God” to cover up the gaping hole left by the process.

      1. Alex_89

        I think your whole article is a misinterpretation of Lewis’ highly acute reasoning on the mechanics of thought. Above, shawn has already explained very well the matter, but your response is what I think must be clarified:
        Babies brains (or whatever other part of the body of whatever living being on earth) are not caused by chance, but by a series of very specific events and reactions. There is not the slightest correlation with chance, only the fact that we can acquire knowledge as we grow up because our brains function in the way they are suppose to function. Now you could say that we have acquired this function of having a proper brain over the millions of years of evolution, by chance, but I must disagree with you because that is not what the biological evidence shows us. Until this very day, scientists havent been able to produce any experiment to sustain the claim that by chance a dna molecule can just be born, let alone a whole cell, let alone a whole living being. The odds are so extremely little, that there are more 0.000…zeros after the comma than the atoms in the whole universe. Even the odds of having a very basic protein (that alone cant do anything, but let’s not consider that) forming by chance from random chemicals is so so tiny that not even 5 billions years are enough for it to be statistically significant (p>000.1). Just one little basic protein! Imagine a whole cell or living organism!
        The odds are against evolution, against life and living beings coming into existence by chance, but as we can all see, life and living beings do exist, and some biological mechanisms are so complex that we havent even discovered them all yet, so logic tells me that life must have arisen in some other way than with chance, and so with a “intelligent and creative mind”
        2) God is not just an intelligence that arrived by chance, as you suggest, he is outside time, space and matter, so by definition because he created time, he is eternal, has no cause or beginning, it’s all-powerful, all-knowing, all-loving and the standard of morality. So this being that is immaterial, eternal, spaceless, timeless, omnipotent, morally perfect, we call it God. I dont know which “god” you were referring to, but that is not God.

  3. DJ Hastings

    I also agree that CS Lewis’s argument is not sound, and it does involve an artificially imposed logic gate. However, I would like to bring up the consideration that in the quote he’s trying to reason with the everyman and not really trying to be highly detailed and rigorous in his argument. Because of this I don’t believe he’s actually making a logic leap on his first point. I think if he were to explain it in more detail it would likely look like this:

    1. Natural selection theory says that traits become emphasized and passed down in a gene pool when these traits are better adapted to survive and thrive in a given environment.

    2. From point 1 we can infer that human thought developed because it was better adapted to survive and thrive in it’s environment.

    3. From point 2 we can infer that human thought processes are likely biased towards that which appears to aid survival and thrival, and against that which appears detrimental to those concerns.

    4. From point 3 we can infer that human thought does not nessesarily lead to objectively true beliefs because of the likely scenario where objective beliefs appear detrimental to survival and thrival.

    Of course, this line of reasoning doesn’t address the fact that there can be higher order beliefs that hold that objective beliefs are always beneficial despite any appearances to the contrary. It also doesn’t address fact that there are entire systems of empiricism, critical thought and peer review that exist specifically to act as checks and balances against these potential biases.

    1. shawn (Post author)

      Thanks for your comment!


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