The Plantinga "Evolutionary argument against naturalism"

[ChrisV]

This is a spinoff thread from the thread about the Plantinga review of Dawkins' "The God Delusion". I thought this was interesting enough and unrelated enough to the original topic that it deserved its own thread.

To paraphrase the argument, Plantinga says that there is no reason to suppose that evolution produces will produce a brain which contains true beliefs, because evolution is only concerned with adaptive behaviours, not with truth about the world. Therefore combining evolution and naturalism leads to a situation in which one's beliefs about the world have a low probability of being true. I am finding it difficult to state this argument clearly because I think it is complete rubbish. Here it is stated in Plantinga's review of Dawkins:

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Since we have been cobbled together by (unguided) evolution, it is unlikely, [Dawkins] thinks, that our view of the world is overall accurate... Like most naturalists, Dawkins is a materialist about human beings: human persons are material objects; they are not immaterial selves or souls or substances joined to a body, and they don't contain any immaterial substance as a part. From this point of view, our beliefs would be dependent on neurophysiology, and (no doubt) a belief would just be a neurological structure of some complex kind. Now the neurophysiology on which our beliefs depend will doubtless be adaptive; but why think for a moment that the beliefs dependent on or caused by that neurophysiology will be mostly true? Why think our cognitive faculties are reliable?

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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.

If this is so, the naturalist has a defeater for the natural assumption that his cognitive faculties are reliable—a reason for rejecting that belief, for no longer holding it. (Example of a defeater: suppose someone once told me that you were born in Michigan and I believed her; but now I ask you, and you tell me you were born in Brazil. That gives me a defeater for my belief that you were born in Michigan.) And if he has a defeater for that belief, he also has a defeater for any belief that is a product of his cognitive faculties. But of course that would be all of his beliefs—including naturalism itself. So the naturalist has a defeater for naturalism; natural- ism, therefore, is self-defeating and cannot be rationally believed.

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There is a more technical description available in this Wikipedia article about the argument.

Here's EvolutionBlog giving the obvious counterargument:

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Plantinga is worried that if our cognitive faculties evolved via a naturalistic, unguided process, then we have no basis for thinking they are providing us with reliable information about the world. This worry is justified only if you imagine that organisms possessing genes that cause them to misperceive reality will consistently outreproduce those who perceive things accurately. In organisms that reproduce slowly, like humans, it will nearly always be the case that those who perceive the world accurately will live longer and reproduce more successfully than those who do not.

That assertion seems so obvious that it is hardly the sort of thing for which one provides evidence. But if evidence is needed, just consider that there are a variety of brain defects that can cause people to misperceive the world around them, and those people routinely have to be protected from themselves. No one has ever enhanced his fitness by taking hallucinatory drugs.

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Plantinga has to some extent anticipated this:

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Plantinga points out that innumerable belief-desire pairs could account for a given behaviour; for example, that of a prehistoric man fleeing a tiger:

Perhaps Paul very much likes the idea of being eaten, but when he sees a tiger, always runs off looking for a better prospect, because he thinks it unlikely the tiger he sees will eat him. This will get his body parts in the right place so far as survival is concerned, without involving much by way of true belief... Or perhaps he thinks the tiger is a large, friendly, cuddly pussycat and wants to pet it; but he also believes that the best way to pet it is to run away from it... Clearly there are any number of belief-cum-desire systems that equally fit a given bit of behaviour.

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But this won't do. It's true that one can construct belief-desire pairs that give the appropriate result. But if belief-desire pairs are chosen randomly, the odds are overwhelming that one of them will eventually be wrong. Therefore, for correct adaptive behaviour in most situations, we need a way to choose between belief-desire pairs in a consistent way. How do we do that? The only way that I can see is to model the external world. This enables us to generalise; I don't have to have separate beliefs about tigers and wolves, say, I can generalise to beliefs about pointy-toothed animals that chase me. There are also certain desires that can be hardwired in because they are almost always useful. The desire to avoid harm to oneself is something that would be a good adaptive behaviour in most circumstances.

Here is Plantinga's alternative explanation of the source of beliefs in the brain:

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From a theistic point of view, we'd expect that our cognitive faculties would be (for the most part, and given certain qualifications and caveats) 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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OK. So the two theories should provide different predictions. If Plantinga's theory is correct, beliefs should be mostly true, and false beliefs should follow no particular pattern. If evolutionary theory is true, our brains should have a pretty good model of the world, but deviate from it in predictable ways. Specifically, there should be methods we use in interpreting the world that are sound and useful when used properly but often misapplied.

This is exactly what we actually see. One good example is the intentional stance. The intentional stance is the way of interpreting the world we use when considering intentional agents. This is very useful for producing adaptive behaviour: We see a tiger running towards us and we understand that it wants to eat us. This is the quickest and easiest way of predicting the tiger's later behaviour. It is so useful that in modern life we continually misapply and overuse the intentional stance. For instance, when I learnt science in school, the teachers would constantly speak of acids "wanting" to donate a proton and hot air "wanting" to rise. They did this because we are all so familiar with the intentional stance that it makes intuitive sense to think of things this way.

Another example of misuse of the intentional stance is mythology and religion itself. People have a distinct tendency to believe, when observing a phenomenon, that the phenomenon is the result of some being's intentions. Phil153 put it this way in a recent thread:

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Why does something always have to be made by someone?

You'd think [censored] like you would have learnt some humility by now, after having been proven wrong about almost everything. No, schizophrenics aren't possessed by demons, you idiots. Simple, impersonal biology. No, the sun isn't driven by turtles or elephants or chariots or Gods. Simple, impersonal physics. No, there ain't some dude in the sky running a lightning and thunder show, who's responsible for all the rain. Just the impersonal forces of nature. You can slaughter all the animals/people you want to appease the weather God(s), your crops won't get a drop more rain, and you'll still be an idiot.

For everything they can't explain, people with your lack of imagination have always postulated a ghost in the machine. And they have ALWAYS been proven wrong.

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Another example of misapplied techniques is the discernment of patterns in the world. It is an important survival skill to be able to quickly do this, and the cost of being wrong about a pattern is likely to be less than the gain from being right. The result is that people consistently over-perceive patterns, as you will have noted when you play poker.

It's clear that an evolutionary explanation of brain formation not only implies that generally our beliefs about the world will be true, but explains exactly why our false beliefs follow predictable patterns. I don't see that the alternative theistic explanation will do this.

EDIT: A couple of examples of mild cases of exactly what Plantinga was talking about - false beliefs that cause correct adaptive behaviour. Many cultures believe that sick people are possessed by evil spirits which can be transferred by contact. Avoiding the sick is a good adaptive behaviour because it avoids spreading bacteria and viruses. Another example is quoted by Douglas Adams in The Salmon Of Doubt. In Bali, local agriculture was done according to a religious temple calendar, with certain actions performed at certain times to appease deities. An attempt was made recently to modernise agriculture there, with disastrous results; the people went back to the old calendar way and balance was restored. In both cases, the reason for the false belief is that the reality of the situation was impossible for the people to know and therefore impossible to model properly. Notice again the tendency to immediately resort to the intentional stance when confronting the unknown.