Can you Trust Your Brain?

Let me introduce you to a new word: Kluge.

Kluge (rhymes with huge) is a term that describes a clumsy, inelegant solution to a problem – a solution that gets the job done, but is by no means pretty or ideal. A great example, for those that have seen Apollo 13, is the contraption the 3 astronauts construct out of duct tape, a sock, and a plastic bag to filter the CO2 in their ship after they loose power. It worked, but I don’t think NASA will be using that exact model in future ships. It was a kluge.

Gary Marcus, a professor in the Department of Psychology at New York University has a forthcoming book titled, Kluge: The Haphazard Construction of the Human Mind. Marcus’ thesis is that your brain is a kluge. Just like that clumsy CO2 filter, it gets the job done, but it is not an efficiently designed solution.

In a column in the L.A. Times, ‘Does your brain have a mind of its own?’ Marcus states, “In the mental machinery that governs our everyday decisions, kluges abound.”

The reason he thinks the brain is such an inefficient machine is that it is the product of evolutionary biology. Marcus’ project is to explain why our brains function the way they do by telling a purely naturalistic evolutionary story about their origin.

The only value that drives evolution is survival power. If a certain adaptation promotes survival, and thus has a greater potential to pass along genes, then it will perpetuate. Survival is king in the evolutionary story. Therefore, since our brains, like everything else about us, have been forged out of the evolutionary process, they are designed to promote our survival and are not necessarily built for the other complex processes that we now ask them to do: things like setting goals, remembering details, or even studying algebra.

In a review of the forthcoming book, writing for Newsweek, Raina Kelley explains:
[Marcus] argues our brains didn’t evolve in a way that allowed us to thoroughly evaluate how well our beliefs represent reality.

So the conclusion Marcus reaches is that “kluges abound” in our brains because they were forged by chance to promote survival but we now ask them to do all kinds of other things than simply alert us to run away from predators. Just like the sock in the CO2 filter, our brain may be able to get the job done (when it comes to forming thoughts that correspond to the world, that is, when it comes to producing true knowledge), but it is inefficient and inelegant since it developed with a different goal in mind: survival.

While I agree with Marcus’ analysis that if our brains are a result of a purely naturalistic evolutionary process then they are inefficient and “kluges abound,” I actually think his premises force him to go even further than he does. If his project is to explain the functioning of the brain from a purely naturalistic evolutionary process, he must admit that the brain is actually not “getting the job done” – that is, the brain is not a reliable producer of true beliefs. Let me explain.

Naturalistic evolutionists assume that the thoughts and ideas the brain produces have actual correspondence to reality, that is, the brain is trustworthy in producing true beliefs. But what is the basis for this assumption on the evolutionary view? The evolutionary view is committed, by definition, to survival being the engine of progress. True beliefs may aid survival, or they may not. And that is exactly the point. True beliefs and survival beliefs are not necessarily the same thing.

We can surely imagine a situation in which believing something false actually helps us survive longer to pass along our genes to the next generation. For example, say one day long ago a caveman’s brain produced the idea that every time he hears thunder it is the voice of god speaking god language telling him to run to the lowest point he could find. This is not a true belief. This does not correspond to reality. Yet we can see how this belief would have survival power because the caveman who believed this would have a smaller statistical probability of being struck by the lighting that always accompanies the thunder because he is at a lower elevation. The brain that produced such a belief, on the naturalistic evolutionary view, would aid in survival and thus be the kind of brain that is passed along to future generations.

Survival beliefs do not necessarily correspond to true beliefs.

Naturalistic evolution acts as a defeater belief for itself. There is no explanation for why the brain is designed to produce true beliefs, only an explanation for why the brain may produce beliefs with survival power. The two are not always the same thing. With no guaranteed connection between our ideas and reality, we have no guarantee the theory of naturalistic evolution (itself an idea produced in the brain) corresponds with reality at all.

Tim Keller, in The Reason for God, asks, “If our cognitive faculties only tell us what we need to survive, not what is true, why trust them about anything at all?”

If we are to have any reasonable confidence that our thoughts actually correspond to reality (which everyone assumes from the start) we must look beyond the naturalistic evolutionary story. We must look to a brain designer, himself rational, who is able to impart truth-correspondence, not merely survival power, to our intellectual faculties.

Many great minds have already made this exact argument, which has come to be known as “the evolutionary argument against naturalism.” My only goal here is to pirate their ideas and present them, again, to you. CS Lewis, for example, uses this line of reasoning in chapter 3 of his book Miracles, ‘The Cardinal Difficulty with Naturalism,’ which I would highly encourage you to read.

But I will leave you with a quote from Alvin Plantinga, the famous Christian philosopher from Notre Dame:

The naturalist can be reasonably sure that the neurophysiology underlying belief formation is adaptive, but nothing follows about the truth of the beliefs depending on that neurophysiology. In fact he’d have to hold that it is unlikely, given unguided evolution, that our cognitive faculties are reliable. It’s as likely, given unguided evolution, that we live in a sort of dream world as that we actually know something about ourselves and our world.


From a theistic point of view, we’d expect that our cognitive faculties would be… reliable. God has created us in his image, and an important part of our image bearing is our resembling him in being able to form true beliefs and achieve knowledge.

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