This is the first in a series of interviews about religion that I will conduct for The Stone. The interviewee for this installment is Alvin Plantinga, an emeritus professor of philosophy at the University of Notre Dame, a former president of both the Society of Christian Philosophers and the American Philosophical Association, and the author, most recently, of “Where the Conflict Really Lies: Science, Religion, and Naturalism.”
The Stone is a forum for contemporary philosophers and other thinkers on issues both timely and timeless.
Is Atheism Irrational?
By GARY GUTTING
(Materialism and Evolution can't be both True)
...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.
...GG: That does seem to be a hard conclusion to accept. But won’t evolution get the materialist out of this difficulty? For our species to have survived, presumably many, if not most, of our beliefs must be true — otherwise, we wouldn’t be functional in a dangerous world.
Materialism can’t be sensibly believed, at least if, like most materialists, you also believe in evolution.
AP: Evolution will have resulted in our having beliefs that are adaptive; that is, beliefs that cause adaptive actions. But as we’ve seen, if materialism is true, the belief does not cause the adaptive action by way of its content: It causes that action by way of its neurophysiological properties. Hence it doesn’t matter what the content of the belief is, and it doesn’t matter whether that content is true or false. All that’s required is that the belief have the right neurophysiologicalproperties. If it’s also true, that’s fine; but if false, that’s equally fine.
Evolution will select for belief-producing processes that produce beliefs with adaptive neurophysiological properties, but not for belief-producing processes that produce true beliefs. Given materialism and evolution, any particular belief is as likely to be false as true.
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 conclusotherion: that both materialism and evolution are true. Maybe you can hold one or the , 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.
This interview was conducted by email and edited.
Gary Gutting is a professor of philosophy at the University of Notre Dame, and an editor of Notre Dame Philosophical Reviews. He is the author of, most recently, “Thinking the Impossible: French Philosophy Since 1960″ and writes regularly for The Stone.
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