Thursday, April 29, 2010

Plantinga's Evolutionary Argument Against Naturalism

I recently read Naturalism Defeated?: Essays on Plantinga's Evolutionary Argument Against Naturalism. In the beginning, Alvin Plantinga briefly explains his evolutionary argument against naturalism. Then there are a collection of essays criticizing his argument. The essays weren't necessarily addressing Plantinga's explanation found at the beginning of the book, but to other presentations Plantinga has published in books and articles on the argument. Then at the end, he responds to the essays. This was a really interesting book on epistemology, but I have to admit that I didn't understand it all. I want to talk about it anyway.

First, lemme give a brief explanation of the argument (or at least my understanding of the argument). First, I'll start with a couple of definitions:

1. Naturalism--the view that the physical cosmos is all there is. There are no ghosts, gods, or supernatural beings.

2. Evolution--the view that life (particularly human life for the purposes of this argument) developed through a process of unguided mutation and natural selection.

Plantinga thinks that if both naturalism and evolution are true, then probability that our belief-producing cognitive faculties are reliable is low or inscrutable. Or, in philoso-geek-speak:

P(R/N&E) is low or inscrutible,

where P stands for probability, R stands for the reliability of our belief-producing cognitive faculties, N stands for naturalism, and E stands for evolution.

Plantinga further thinks that, as a consequence, anybody who believes in both naturalism and evolution has a defeater for their belief in the reliability of their belief-producing cognitive faculties. And, if they can't trust their belief-producing cognitive faculties, then they can't be rational in holding to naturalism, evolution, or anything else that is the result of their belief-producing cognitive faculties. So, believing in both naturalism and evolution is self-refuting.

Plantinga further argues that this defeater of the reliability of their cognitive faculties cannot be defeated because the only way to defeat it is to rely on one's cognitive faculties to do so.

Now I want to explain why Plantinga thinks P(R/N&E) is low or inscrutable. If there were a God (i.e. if naturalism were false), but we evolved through purely natural cause and effect, then it's still possible for our belief-producing cognitive faculties to be reliable. After all, it's possible that the origin of life was like a cue ball that when hit causes all the other balls to go exactly where the pool player intends them to go through perfectly natural cause and effect. He doesn't have to intervene anymore after hitting the cue ball. Perhaps God got things going, but then things evolved in such a way that our cognitive faculties are reliable. If so, then we could trust our cognitive faculties because God would guarantee them. So naturalism is necessary to make Plantinga's argument work. Evolution alone won't do it.

But naturalism alone won't do it either. If our cognitive faculties came about through some unknown process, maybe the process would guarantee their reliability somehow even though there was no God to have a purpose in any of it. So it's the combination of naturalism and evolution that Plantinga thinks renders our cognitive faculties unreliable.

Now, given naturalism, lemme explain why he thinks evolution is not likely to produce reliable cognitive faculties. It's because natural selection chooses adaptive behavior. It only cares about our cognitive faculties insofar as our cognitive faculties have some causal influence over our behavior.

And there are different views about that among naturalists. One view is called epiphenominalism. That's the view that all of our mental states are caused by our brains, but that the causation does not go the other way around. Our mental states (e.g. our beliefs and desires) cannot cause anything in our brain. Now, if that view is true, then obviously our minds have no causal influence over our behavior. It's easy to see why, in that case, P(R/N&E) would be low or inscrutable. Since our behavior would have nothing to do with our cognitive faculties, and natural selection only cares out about behavior, then natural selection would not care about our cognitive faculties. Our cognitive faculties would be irrelevant to whether we were naturally selected or not.

In another view (don't know the name), it is possible for our minds to have causal influence over our brains. But there are two sub-views under this view. One is that our minds have causal influence over our brains because of their syntax, and the other because of their semantics. By "syntax," I mean the structure of the brain that produced the mental event or that is associated with the mental event. By "semantics," I mean the actual content of the mental event--the actual belief or desire--or the "aboutness" of the mental event.

Let me see if I can explain that a little better. The difference is like the difference in whether a book has causal influence because of the physical properties of the ink and paper or whether it has causal influence because of the meaning of the words in the book.

Now if it turns out that our minds only have syntactical influence over the brain, but not semantical, then again, it's easy to see why this would make P(R/N&E) low or inscrutable. Natural selection would only care about the physical structure of the brain associated with a mental event because that is what results in behavior. It wouldn't care about the content of the mental event. If the physical structure of the brain is all that matters, then it wouldn't matter whether your beliefs were true or false.

Only if our minds have causal influence over our brains by virtue of semantics will natural selection care about our beliefs and our desires.

By the way, I'm using "care" anthropomorphically. Don't read too much into that.

So it's this last view that has any hope of giving us reliable cognitive faculties--cognitive faculties that will produce mostly true beliefs rather than false beliefs. But the only way for evolution to produce reliable cognitive faculties is if it turns out that true beliefs are more likely to result in adaptive behavior than false beliefs. If false beliefs are just as likely to result in adaptive behavior as true beliefs, then it would be easy to see how evolution would produce unreliable cognitive faculties.

Plantinga argues that it's easy to come up with combinations of false beliefs and desires that would result in adaptive behavior. They can be silly, too, because all we're interested in is getting our body parts to the right place to ensure our survival and reproductivity. Suppose, for example, that a tiger is chasing you. You believe tigers are harmless, cuddly, fun animals who love to play chase, and such is your desire to play with said tiger that you run from it. Although the belief is false, it gets your body parts where they need to be to stay alive. Or let's take something even more silly. Let's say you believe the tiger is sweet, you want to hug it, and you believe the best way to hug it is to run from it. It's an absurd belief, but it gets you where you need to go to stay alive. And it's not hard to come up with scenarios like this. For any situation a person can bring up in which they might claim that some true belief resulted in adaptive behavior, you can come up with an absurd belief that would have the same result. So, argues, Plantinga, evolution is not likely to produce reliable cognitive faculties.

The most common objection that I half way understood was that although given evolution and natural selection alone, our cognitive faculties might be unreliable, it could be there are other factors which, when combined with naturalism and evolution, would increase the probability that our cognitive faculties are reliable. In other words...

P(R/N&E) may be low or inscrutable, but P(R/N&E&C) might be high.

I don't remember what suggestions were given for C, but I remember some of the critics pointing out that we have an intuition about the reliability of our cognitive faculties that overcomes any argument to the contrary. There's a kind of Descartian clearness and distinctness about our cognitive faculties.

Plantinga didn't respond to that the way I expected him to. What I would've said was that, yeah, sure. I totally agree that our cognitive faculties are reliable. That's not my point. My point is that if our cognitive faculties were the result of naturalistic evolution, then they would not be reliable. Since they are reliable, then either naturalism is false, evolution is false, or they're both false. Here's the syllogism:

1. If N&E are true, then our cognitive faculties are unreliable.
2. Our cognitive faculties are not unreliable.
3. Therefore, either N is false, E is false, or they're both false.

But that's not how Plantinga responded. I'd tell you how he responded, but I don't remember.

Another objection I remember was that although it's easy to come up with individual cases of where a false belief might produce adaptive behavior, it doesn't follow that our beliefs could be systematically false and still result in adaptive behavior. Now this, I kind of agreed with. One of the problems I had with Plantinga's argument before I read this book is that it just seemed likely to me that, as a whole, true beliefs are more likely to produce adaptive behavior than false beliefs, even if it turns out that in some cases, false beliefs might produce adaptive behavior. Because cognitive faculties don't just produce individual beliefs. They produce kinds of beliefs.

In the past, Plantinga has responded to this kind of argument by giving an example of how a systematically false kind of belief can still result in adaptive behavior. For example, suppose you believed that everything was a witch, including inanimate objects. Your cat is a witch, your car is a witch, etc. You might believe that witch hamburger is tasty or that witch girl is a cutie and none of these beliefs would result in behavior that was any different than if you didn't have these beliefs. So almost all of your beliefs would be false, but they would still result in adaptive behavior.

One of the critics pointed out that all of these false beliefs can be broken down into true and false beliefs. For example, "That witch hamburger is tasty," can be broken down into, "That object is a witch," and "That object is a kind of hamburger," and "That object tastes good." So you've got two true beliefs and one false belief.

I want to stray away from this book a little now and share a thought I've had for a while since I first heard Plantinga's argument. I've noticed that in a lot of debates between theists and atheists over morality that atheists will explain our morality by appealing to evolution, or at least social evolution. Moral beliefs produce adaptive behavior. That's why we developed into moral creatures. There's no reason to suppose there's any divine law behind these moral instincts.

Think about that. Atheists who argue this way aren't saying that objective moral values emerged through evolution. Quite the opposite. They are denying the existence of objective moral values on the basis that our moral beliefs are the result of evolution. Essentially, they are conceding one of Plantinga's primary arguments--that if our belief-producing cognitive faculties are the result of evolution, then we cannot trust their reliability. It's because evolution produced our belief in morality that somehow calls their reliability into question. But if that's the case, then why stop at morality?

Which is more likely--that evolution would result in reliable belief-producing cognitive faculties or that it would result in unreliable belief-producing cognitive faculties? If reliable, then shouldn't we all embrace the existence objective moral values since that seems to be our most natural inclination? But if unreliable, then why not admit that our belief in naturalism and evolution are both irrational? In fact all of our beliefs are irrational?

But that brings me back to the book and a thought I had while reading it. This is another objection I had to Plantinga's argument. If it turns out that a person who believes in both naturalism and evolution is rationally obliged to believe that the reliability of their belief-producing cognitive faculties is low or inscrutable, then shouldn't they doubt that conclusion? It seems like if Plantinga's argument is sound, then a person could never rationally come to the conclusion that they are irrational because it would require them to reason rationally. How could they trust that naturalism and evolution are incompatible with the reliability of their cognitive faculties if their cognitive faculties are being called into question? Do you know what I'm saying?

Near the end of the book, I was happy to find that Plantinga noticed this problem, too, and he addressed it. He didn't really solve the problem so far as I could tell (or that I can remember). He just discussed it. It leads to an infinite loop.

That's about all I have to say. My apologies to Alvin Plantinga and all the essay writers for that book if I've butchered any of your views. I fully admit that I didn't understand everything I read. But it was really interesting! And I will probably read it again at some point.

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