Stupid Arguments Christians Should Avoid #51: 3 Stupid Arguments from Alvin Plantinga (3 of 3)

Stupid Arguments Christians Should Avoid #51: 3 Stupid Arguments from Alvin Plantinga (3 of 3) March 2, 2020

Alvin Plantinga is a professor emeritus from Notre Dame. Given that he is a philosopher, you’d expect better arguments than these three that he used in a New York Times interview.

You’d expect wrong.

I wondered if these were casual arguments, tossed out without much thought during a live interview. Could that explain why they were so poor? Nope: the original article makes clear that this interview was done by email, so Plantinga’s answers were presumably carefully considered.

Let’s move on to the final argument that I will be critiquing (part 1 here). (And there are more. Read the original interview if you want more weeds to chop down.)

#3. Evolution gives us beliefs that are just as likely to be false as true

The interviewer said, “So your claim is that if materialism is true, evolution doesn’t lead to most of our beliefs being true.”

Plantinga replied:

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.

Huh? Why imagine that beliefs are as likely to be false as true? We’ve seen this odd thinking before in his Evolutionary Argument Against Naturalism (I respond to that argument here). He begins with the valid observation that beliefs honed by evolution are useful for survival but don’t need to be true. (I’d argue that supernatural beliefs are an example.) His illustration is an imaginary Neolithic man who believes two odd things: that tigers are cuddly and that the best way to pet a tiger is to run away from it. The first belief is bad for survival and the second is false, but these two beliefs combine into a protective pair.

But why imagine it ends there? If every belief is a roll of the dice, our primitive man would have no beliefs shaped by reality. He might respond to sleepiness by drinking water, to thirst by finding a warm place, to cold by getting out of the sun, and so on. He’s too dumb to live, and that’s where evolution comes in. Reality is a demanding mistress, and beliefs not in accord with reality are judged harshly. If your beliefs for finding food, water, and shelter don’t fit well with reality, evolution will have something to say about it.

Plantinga clearly has little difficulty sifting true survival beliefs from false ones, and he’ll agree that we are all pretty good at this, too. And yet his hypothetical primitive man isn’t. I assume Plantinga concludes, via reductio ad absurdum, that such a man couldn’t exist, so therefore God must step in to impose correct beliefs on us. If evolution can’t be trusted to work for human beliefs, the same must be true for other animals, so God must impose survival beliefs on them, too.

I think I’ll go with the consensus view of the people who understand the evidence, not non-biologist Alvin Plantinga.

Extrapolate to many beliefs

There’s one more bit of childish logic that needs to be addressed.

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.

First, our beliefs aren’t independent. When one belief has proven itself to be reliable through repeated use, we might build on that foundation by trying out additional provisional beliefs.

Second, it’s true that the more imperfect beliefs you collect, the likelier that one or more are false. Plantinga’s probability of 0.0004 for 67 out of 100 beliefs to be true may be correct when these tenuous beliefs have only a probability of 0.5 of being true. Survival beliefs, whether instinctive (“things that smell bad can make you sick if you eat them”) or taught (“prey animals tend to congregate at water holes at dawn and dusk”), usually have a probability of being true far higher than 0.5.

And finally, Christians and atheists all agree that human brains are imperfect. They can be changed by an injury, drugs, or a tumor. They’re subject to mental illness, dementia, biases, and illusions. They work less well when we’re hungry, stressed, or tired. (The story of Phineas Gage is a dramatic illustration that the mind is a product of a physical brain and nothing more.)

Plantinga is correct that our brains are imperfect, but then he proposes that Christians believe them when they report that God exists? The Christian claims are about the most ludicrous possible, and they need a mountain of evidence. Plantinga doesn’t have it.

Instead of faith, science compensates for our imperfect hardware with the scientific method. Conclusions are always tentative. There are rewards for overturning the consensus view. The result is science’s imperfect but still prodigious track record of results. Religion has, not a poorer track record, but no track record of teaching us new things about reality.

These three arguments add to the pile of really poor apologetics from famous Christians. I hope they provided a little practice for you and that you’re now better prepared in case you come across them in the future.

Perhaps the most optimistic spin I can put on this exercise is Catherine Aird’s observation, “If you can’t be a good example, then you’ll just have to be a horrible warning.”

If this is the best that theology can do,
theology is in big trouble.
— Dr. Massimo Pigliucci,
in response to this interview of Alvin Plantinga


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