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Something I’ve been wanting to tackle for a long time is Alvin Plantinga’s Evolutionary Argument Against Naturalism which he presented to a Christian lay audience in an article published online in Christianity Today. Here’s a spoiler: it’s awful. According to Plantinga,

As I see it, this is a whopping error: evolution and naturalism are not merely uneasy bedfellows; they are more like belligerent combatants. One can’t rationally accept both evolution and naturalism; one can’t rationally be an evolutionary naturalist. The problem, as several thinkers (C. S. Lewis, for example) have seen, is that naturalism, or evolutionary naturalism, seems to lead to a deep and pervasive skepticism. It leads to the conclusion that our cognitive or belief-producing faculties—memory, perception, logical insight, etc.—are unreliable and cannot be trusted to produce a preponderance of true beliefs over false.

I have no problem with skepticism. I think everybody should be a skeptic. For those who don’t, I’m offering up the Brooklyn Bridge… Cheap!

Nor do I have a problem with anything in that last long sentence. Our memory is quite fallible. So is our ‘logical insight’, since it is based on heuristic and not rigorous logic. It just happens to work most of the time and is fast, and for the times it doesn’t it typically doesn’t matter. For instance, our natural instinct when out in the dark we hear a rustling in the bushes our impulse is to take flight. But whether the rustling in the bushes is a real danger (the tiger that Plantinga likes to use) or a prankster is not considered by our subconscious. With the former, our chance of survival increases because we don’t go over to the bush to check the source of the disturbance. With the latter, we just feel foolish. In both cases, our lives continue.

And this is one of the problems with Plantinga’s argument, one I have not seen elsewhere. He seems to confuse impulses such as the fight-or-flight one in the example above, with beliefs born of our cognitive faculties. The former is not based on belief, but is a simple response to sensory input. It’s dark, therefor we are on our guard already (‘primed’, as behavioral psychologists would say). Our eyes are evolved for moving around in daylight, so our sensory input is limited making us uneasy. So anything that startles us is going to produce that fight-or-flight response. No belief is necessary at all, since it is hardwired into our brains. Another related point where Plantinga is apparently confused is that it is not beliefs that evolve. It is our cognitive ability to generate beliefs that evolved. Beliefs such as ‘fire is hot’ are learned beliefs. Similarly, naturalism and evolution were not born from evolutionary processes, but from observation and experiment.

Plantinga has some other strange beliefs about beliefs. He writes,

So consider any particular belief on the part of one of those creatures: what is the probability that it is true? Well, what we know is that the belief in question was produced by adaptive neurophysiology, neurophysiology that produces adaptive behavior. But as we’ve seen, that gives us no reason to think the belief true (and none to think it false). We must suppose, therefore, that the belief in question is about as likely to be false as to be true; the probability of any particular belief’s being true is in the neighborhood of 1/2. But then it is massively unlikely that the cognitive faculties of these creatures produce the preponderance of true beliefs over false required by reliability. If I have 1,000 independent beliefs, for example, and the probability of any particular belief’s being true is 1/2, then the probability that 3/4 or more of these beliefs are true (certainly a modest enough requirement for reliability) will be less than 10(to the power -58). And even if I am running a modest epistemic establishment of only 100 beliefs, the probability that 3/4 of them are true, given that the probability of any one’s being true is 1/2, is very low, something like .000001. So the chances that these creatures’ true beliefs substantially outnumber their false beliefs (even in a particular area) are small. The conclusion to be drawn is that it is exceedingly unlikely that their cognitive faculties are reliable.

PZ Myers has also focused in on this passage and for the same reason that I was originally struck dumbfounded. Plantinga claims that any particular belief “is about as likely to be false as to be true”. I’ve seen this coin flip false analogy all over the place. With a coin, we know there are two distinct possibilities when flipped (ignoring the third one, the possibility of the coin landing on edge). There is nothing to distinguish between the two possibilities- not because we have no knowledge of the truth value of each of the two possibilities as with the random beliefs Plantinga is describing, but because we do know everything about the system and still have no way to predict the outcome. (We could, of course, increase our odds to near certainty using physics once the coin is tossed.) For any belief in the absence of supporting evidence as Plantinga describes above, I would give odds (if I had to- assigning probabilities demands that we actually know something about the truth of the belief in the first place) for any given belief not 1/2, but more towards 0. Indeed, I would place the probability at 0 till I have some reason to discard the null hypothesis (i.e., that the belief is false) in favor of the claim.

We know many beliefs are whacky: homeopathy, UFO sightings, faith healing, astrology, psychics- the list of demonstrably false beliefs is depressingly endless. If Plantinga had ever read either Bruce Hood’s SuperSense: Why We Believe in the Unbelievable or Gary Marcus’ Kluge: The Haphazard Evolution of the Human Mind he would never have come up with this nonsense. False beliefs are the norm!

What differentiates what we can be pretty confident are false beliefs from those that we can be confident that they are true? Evidence, of course! And this is what Plantinga bizarrely ignores. I mean, seriously! How could he have missed this? Was it purposeful obfuscation? Or just selective blindness to this issue? As I implied above, it is impossible to attach an confidence to a given belief if there is no evidence in support.

PZ Myers noted the same problem: a belief is only as good as the supporting evidence. He writes:

In Plantinga’s world, if we queried the inhabitants with some simple question, such as, “Is fire hot?”, 50% would say no, and 50% would say yes. This world must be populated entirely with philosophers of Plantinga’s ilk, because I think that in reality they would have used experience and their senses to winnow out bad ideas, like that fire is cold, and you’d actually find nearly 100% giving the same, correct answer. Plantinga does not seem to believe in empiricism, either.

And that is the wooden stake through the heart of Plantinga’s EAAN. Plantinga completely ignores epistemology. Why do we value some beliefs more than others? Evidence, my friends- evidence. And in my experience, those beliefs supported by empirical evidence have by far the greatest truthiness about them. The ‘scientific method’, as far as has been demonstrated, is not only the best way to verify beliefs, but is the only way. I would even go farther and say that naturalism nor evolution are more than just belief. They are conclusions drawn from many lines of evidence. If you think otherwise, Dara O’Briain has a sack waiting for you.

According to Plantinga,

If evolutionary naturalism is true, then the probability that our cognitive faculties are reliable is also very low. And that means that one who accepts evolutionary naturalism has a defeater for the belief that her cognitive faculties are reliable: a reason for giving up that belief, for rejecting it, for no longer holding it.

First, that we can not trust conclusions born of our cognitive faculties does not negate them! Indeed, I would say it is random beliefs that are completely untrustworthy. There have to be reasons to hold beliefs based on evidence and reason. Second, if evolutionary processes shaped an intellect which could not reason properly or at least a facsimile thereof, it would be maladaptive and weeded out quickly. Thus, his assertion ‘the probability that our cognitive faculties are reliable is also very low’ just does not pass muster and I suggest it is based on his coin flip false analogy. Plantinga seems to think that our cognitive faculties always produce true beliefs. Of course, Plantinga needs this to be so not just in order to present his argument, but to maintain his own belief in his god. But the assertion is simply ridiculous in light of all the strange beliefs flying around. Including his.

Worse, he seems to think that specific beliefs are coded for, such as “I believe I should race tigers”. But DNA simply doesn’t have the storage space for such inefficiency. Instead, evolution stumbled upon generic abilities, such as the abilities to hold beliefs and to be able to reason. Those who engage in tiger racing will not be able to reason that tigers are a potential danger and thus not get a fear response. That doesn’t seem very optimal. Nor will they reason that tigers are a danger to kin and will thus not protect family from tigers. Nor will they – given the opportunity – seek to escape a rampaging tiger, say, climbing a nearby tree. Any who can not reason thus will be cat food.

Thus, while our reason may be fallable, it is difficult to fathom how it is not correct far more than it is in error. The same with our senses. It is difficult to understand how being presented with an inaccurate representation of our environment would not be weeded out by natural selection. Plantinga’s arguments simply don’t stand up to any scrutiny and betray his rather strange understanding (if I can call it that) of natural selection. In fact, it is difficult to see how holding wrong beliefs aren’t maladaptive, since they are wasteful and can lead to serious risk.

Evolution shaped our brains and hence our intellect to model our surroundings. Plantinga does not dispute this, just that we can not trust our interpretation of the model. But we can verify it. We can test it. As children we generated a belief that ‘fire is hot’ from interacting with the world. We avoid getting too close to the flames because our experience tells us that it can burn us and not because of some maladaptive false belief.

Plantinga believes that the major objection to his argument is exactly this. He writes in response,

But of course we can’t just assume that they are in the same cognitive situation we think we are in. For example, we assume that our cognitive faculties are reliable. We can’t sensibly assume that about this population; after all, the whole point of the argument is to show that if evolutionary naturalism is true, then very likely we and our cognitive faculties are not reliable. So reflect once more on what we know about these creatures. They live in a world in which evolutionary naturalism is true. Therefore, since they have survived and reproduced, their behavior has been adaptive. This means that the neurophysiology that caused or produced that behavior has also been adaptive: it has enabled them to survive and reproduce. But what about their beliefs? These beliefs have been produced or caused by that adaptive neurophysiology; fair enough. But that gives us no reason for supposing those beliefs true. So far as adaptiveness of their behavior goes, it doesn’t matter whether those beliefs are true or false.

But, as I have written above, there is nothing here which necessitates that beliefs are false. This is a requirement for defeating naturalism. Thus, the argument is equivocal. You can’t show they are true, you can’t show they are false. At least you can’t in any way which is presented in the article. It is what is not in the article and discussed above which we should all use in guiding our beliefs: evidence! At best, if I thought his argument had merit, it would only undermine naturalism. But, to put it euphemistically, he’s simply and demonstrably WRONG!

Plantinga claims that Christians don’t have any of these ‘problems’. He writes,

Clearly this doubt arises for naturalists or atheists, but not for those who believe in God. That is because if God has created us in his image, then even if he fashioned us by some evolutionary means, he would presumably want us to resemble him in being able to know; but then most of what we believe might be true even if our minds have developed from those of the lower animals.

I suppose they don’t, if one ignores the sticky problems of demonstrating that any god exists, how said god(s) went about ‘creating us in his image’, yada, yada, yada. And how does he know his belief that god “would presumably want us to resemble him in being able to know”? What if his god really just wanted a really big Barbie set to play with? This is just presupposition based on wishful thinking and isn’t philosophy at all.

He concludes,

The obvious conclusion, so it seems to me, is that evolutionary naturalism can’t sensibly be accepted. The high priests of evolutionary naturalism loudly proclaim that Christian and even theistic belief is bankrupt and foolish. The fact, however, is that the shoe is on the other foot. It is evolutionary naturalism, not Christian belief, that can’t rationally be accepted.

Well, Alvin, let me tell you. Your self-congratulatory back-slapping is premature. I don’t think either naturalism or evolution is in any threat over this. As PZ Myers wrote,

He’s reduced to a bogus either/or distinction. Either we are organic machines that evolved and our brains are therefore collections of random beliefs, or — and this is a leap I find unbelievable — Jesus gave us reliable minds. Seriously. That’s what his argument reduces to.

A bit glib, perhaps, but it captures the essence of the argument, and it is a terrible argument, a sad footnote in the career of someone who has significantly contributed to the field of philosophy.

And for those who would like to get into the nitty-gritty philosophy, Stephen Law has a great refutation online here, which was published in the journal Religious Studies.



  1. See, the ‘coin-flip’ logic is hilarious to me, because of John Stewart. He had a piece about some religious fundies that hated the Large Hadron Collider, and used that logic to claim that it would destroy the world. (I.E there are two possibilities, it can destroy everything or it will not destroy everything, thus, there is a 50% chance of it happening)

    John Oliver asks the guy if the LHC makes a black hole, would they consider having sex to make a new generation, because, by the same logic, there’s a 50% chance of gay sex resulting in a child.

    Yeah, you’re right, naturalism is not threatened by this non-sense.

    • Yeah, that there are two possibilities means that they are of equal probability in outcome is a red herring. Sure, the LHC might be able to make baby black holes. That would actually be awesome. But they would evaporate almost instantaneously! A little bit of knowledge makes people stupider it seems.

  2. I have never had any respect for Plantinga’s writing and do not understand why he is as well known as he is. He is just making philosophers look bad by making people think that he is somehow indicative – witness PZ’s remarks.

    • I discussed the article from Christianity Today with a member of the faculty of philosophy at the U of Calgary. She related to me some of the decent contributions he has made in certain areas of philosophy (non-theological ones), but for this she used the word “senile” to describe him. Enough said. It’s a terrible argument- Plantinga just doesn’t understand how the brain evolved. I think it’s quite clear that not all beliefs should be trusted, which is exactly why we skeptics clammer for EVIDENCE!

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