Saturday, May 24, 2014

My First Look at Plantinga's Evolutionary Argument Against Naturalism

Gary Gutting continues to probe Alvin Plantinga at Is Atheism Irrational? by asking

...isn’t the theist on thin ice in suggesting the need for God as an explanation of the universe?

Plantinga replies weakly:

Some atheists seem to think that a sufficient reason for atheism is the fact ... that we no longer need God to explain natural phenomena...

As a justification of atheism, this is pretty lame. We no longer need the moon to explain or account for lunacy; it hardly follows that belief in the nonexistence of the moon (a-moonism?) is justified.

It’s almost as if Plantinga didn’t take this interview seriously. He missed the point early in the interview when he gave a detailed criticism of Russell’s Teapot, but ignored the broad parody that it intends. The “a-moonist” example above is worse yet. He should have skipped this lunacy (pun intended) and gone straight to his claim that

The most important ground of belief is probably not philosophical argument but religious experience.

Okay then! We’ve finally arrived at what the estimable Dr. William Lane Craig calls “not really an argument”. If I may interpret this, he’s saying that there’s good reason to believe because you believe you’ve experienced something. Meh.

He then proceeds to give some (psychological) reasons why non-believers might not believe. Double meh.

At this point, Gutting nudges Plantinga into a discussion of materialism, and Plantinga takes the bait.

GG: ... atheists ... think there’s nothing beyond the material entities open to scientific inquiry, so there there’s no place for immaterial beings such as God.

AP: Well, if there are only material entities, then atheism certainly follows. But there is a really serious problem for materialism: It can’t be sensibly believed, at least if, like most materialists, you also believe that humans are the product of evolution.

Thus begins what I believe is a Reader’s Digest version of Plantinga’s Evolutionary Argument Against Naturalism (EAAN). I’m going to wuss out and quote more of this verbatim in order to avoid clipping out important subtleties. Here he outlines his conception of beliefs:

First, if materialism is true, human beings, naturally enough, are material objects. Now what, from this point of view, would a belief be? My belief that Marcel Proust is more subtle that Louis L’Amour, for example? Presumably this belief would have to be a material structure in my brain, say a collection of neurons that sends electrical impulses to other such structures as well as to nerves and muscles, and receives electrical impulses from other structures.

But in addition to such neurophysiological properties, this structure, if it is a belief, would also have to have a content: It would have, say, to be the belief that Proust is more subtle than L’Amour.

He goes on to what (I believe) is the heart of his argument:

I’m interested in the fact that beliefs cause (or at least partly cause) actions. For example, my belief that there is a beer in the fridge (together with my desire to have a beer) can cause me to heave myself out of my comfortable armchair and lumber over to the fridge.

But here’s the important point: It’s by virtue of its material, neurophysiological properties that a belief causes the action. It’s in virtue of those electrical signals sent via efferent nerves to the relevant muscles, that the belief about the beer in the fridge causes me to go to the fridge. It is not by virtue of the content (there is a beer in the fridge) the belief has.

So far, I believe he’s saying that the belief and the action are not materially related.

...This means that the content of the belief isn’t a cause of the behavior.

Gutting and Plantinga go on to banter about whether evolution can produce beliefs that are true, or merely adaptive - as Plantinga claims. The last few paragraphs of the interview are worth quoting in full:

GG: So your claim is that if materialism is true, evolution doesn’t lead to most of our beliefs being true.

AP: Right. In fact, given materialism and evolution, it follows that our belief-producing faculties are not reliable. Here’s why. If a belief is as likely to be false as to be true, we’d have to say the probability that any particular belief is true is about 50 percent. Now suppose we had a total of 100 independent beliefs (of course, we have many more). Remember that the probability that all of a group of beliefs are true is the multiplication of all their individual probabilities. Even if we set a fairly low bar for reliability — say, that at least two-thirds (67 percent) of our beliefs are true — our overall reliability, given materialism and evolution, is exceedingly low: something like .0004. So if you accept both materialism and evolution, you have good reason to believe that your belief-producing faculties are not reliable.

But to believe that is to fall into a total skepticism, which leaves you with no reason to accept any of your beliefs (including your beliefs in materialism and evolution!). The only sensible course is to give up the claim leading to this conclusion: that both materialism and evolution are true. Maybe you can hold one or the other, but not both.

So if you’re an atheist simply because you accept materialism, maintaining your atheism means you have to give up your belief that evolution is true. Another way to put it: The belief that both materialism and evolution are true is self-refuting. It shoots itself in the foot. Therefore it can’t rationally be held.

That’s the end of the interview, with Plantinga concluding that an atheist can’t believe in evolution because it can’t produce true beliefs, thus is self-refuting. Well!

Let me take a crack at this. There are a lot of phrases and sentences that deserve specific criticism, but it’s not worth getting mired down in details because I think he’s wrong at a more general level.

My most recent thought is simply that evolution doesn’t have to produce beliefs that are true, only animals that survive and reproduce, and can eventually hone their beliefs. Then when an animal like Homo sapiens is successful enough to do more than just survive and reproduce, it just needs to have the potential to develop beliefs that are more true than not, and must be able to do this in the space of a lifetime. If these truer-belief-developing animals are able to survive in greater numbers than non-truer-belief-developing animals, then over time, most will have that potential, and - because this particular animal developed culture - culturally the practices that take advantage of this material potential to develop truer beliefs are institutionally reinforced, institutionally passed on to descendants, and further propagated. It is that tipping point where an animal can develop a mostly true belief, coupled with the development of culture, that speeds the adoption of mostly true beliefs which, over generations, get refined until they become almost-certainly-true-beliefs. Nothing magical required. If this guy’s a great philosopher of theology, I don’t see it.

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