Plantinga's Evolutionary Argument Against Naturalism

Plantiga's argument can be found here:

https://www.bethinking.org/atheism/an-evolutionary-argument-against-naturalism

Now for the argument that it is irrational to believe N&E: P(R/N&E) is either low or inscrutable; in either case (if you accept N&E) you have a defeater for R, and therefore for any other belief B you might hold; but B might be N&E itself; so one who accepts N&E has a defeater for N&E, a reason to doubt or be agnostic with respect to it. If he has no independent evidence, N&E is self-defeating and hence irrational.

It can be summed up (from here):

(1) P(R/N&E) is low. 

(2) Anyone who accepts (believes) N&E and sees that P(R/N&E) is low has a defeater for R.

(3) Anyone who has a defeater for R has a defeater for any other belief she thinks she has, including N&E itself.

(4) If one who accepts N&E thereby acquires a defeater for N&E, N&E is selfdefeating and cannot rationally be accepted.

To explain "P(R/N&E)", that means the probability of R (our cognitive faculties are reliable), if we assume N&E (naturalism and evolution) is true.

Do we have reliable cognitive faculties?

My first point is that we have reliable cognitive faculties, and we know that without any regard as to where those cognitive faculties come from.

We can trust our faculties because they have a track record of working, not because of their origin.

Some of this discussion hangs on what is meant by reliable. If we are right 98% of the time, does that count as reliable? I think Plantinga is tacitly assuming 100% reliable, but he never says that - because he knows we get stuff wrong sometimes.

If creationism is true, and we were made by a perfect God is his image, we would expect perfectly reliable cognitive faculties. We do not have that.

I think evolution selects for a brain/mind that is good at creating true beliefs, but evolution produces things that are good enough to give the individual an advantage, not that are perfect. The eye is a great example of something that is good enough but has some serious flaws, such as the blind spot. It is easily damaged and deteriorates with age, but it is good enough to serve us well for long enough for us to raise a family and pass our genes to the next generation.

Our cognitive faculties are good enough to serve us well, but not perfect.

Also worth noting that 99% of biologists accept evolution. If their cognitive faculties are reliable then we can be pretty sure evolution is true!

If the premise is true

Let us suppose his premise, that P(R/N&E) is low, is true. Does the argument follow?

It does not, and the reason for that is all about the nature of probability. If naturalism and evolution are true, then the outcome was decided long ago. When cognitive faculties first evolved, either they were reliable or they were not, and either way mankind is now stuck with what we have. Such is the way of evolution.

This is like rolling dice. We can suppose that our cognitive faculties being reliable was like rolling double six a million years ago, while any other rolls would mean our cognitive faculties are NOT reliable.

Where we are right now, that probability is irrelevant. Right now we have good evidence to suppose we have reliable cognitive faculties. We have good reason to suppose way back then, we rolled double six. Sure, P(R/N&E) is low, but it happened anyway.

Plantinga's argument is that that probability was very low, but so what? Whether the probability was 50/50 or 1 in 36 or even 1 in a million, we got lucky and have reliable cognitive faculties. And whatever that probability was, it does not impact what we believe today.

And anyway it is not true

Bear in mind that even some bacteria can swim, and they do so in a direction that is beneficial - more food, less danger, whatever. Seems pretty obvious that bacteria that swims towards food and away from danger will survive better than bacteria that swim in a random direction. Even for bacteria a "world view" that is accurate is a survival advantage - though obviously bacteria do not have beliefs.

Plantinga holds that evolution selects for behavior, not belief. The behavior of the bacteria gives it an advantage, though it has no beliefs behind it. From this, Plantinga takes a great leap to suppose having erroneous beliefs that lead to advantageous behavior is considerably more likely than having the correct belief lead to advantageous behavior - i.e., P(R/N&E) is low.

Beliefs don't causally produce behavior by themselves; it is beliefs, desires, and other factors that do so together. Then the problem is that clearly there will be any number of different patterns of belief and desire that would issue in the same action; and among those there will be many in which the beliefs are wildly false. Paul is a prehistoric hominid; the exigencies of survival call for him to display tiger avoidance behavior. There will be many behaviors that are appropriate: fleeing, for example, or climbing a steep rock face, or crawling into a hole too small to admit the tiger, or leaping into a handy lake. Pick any such appropriately specific behavior B. Paul engages in B, we think, because, sensible fellow that he is, he has an aversion to being eaten and believes that B is a good means of thwarting the tiger's intentions.​

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But clearly this avoidance behavior could result from a thousand other belief-desire combinations: indefinitely many other belief-desire systems fit B equally well. 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 that 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. Or perhaps the confuses running towards it with running away from it, believing of the action that is really running away from it, that it is running towards it; or perhaps he thinks the tiger is a regularly reoccurring illusion, and hoping to keep his weight down, has formed the resolution to run a mile at top speed whenever presented with such an illusion; or perhaps he thinks he is about to take part in a 1600 meter race, wants to win, and believes the appearance of the tiger is the starting signal; or perhaps .... Clearly there are any number of belief-cum-desire systems that equally fit a given bit of behavior.​

There are several flaws here.

1. One place this breaks down is that we, the descendants of Paul, know that tigers are dangerous. This ties in with my previous point; even if the probability of that is very low, we know it happened.

2. I would suggest that Paul has this belief about tigers because he has a more general belief that animals with big teeth and claws are dangerous, and that that belief originates from seeing people mauled by said animals. Whereas it is hard to imagine where he could get the idea that the appearance of a tiger indicates the start of a race.

That is, it would seem more reasonable to suppose a correlation between belief and reality. We can see how reasoning could get from tiger appearing to danger present, but not from tiger appears to race has started.

3. I do not dispute that there are "any number of belief-cum-desire systems that equally fit", but to think each is equally likely is just nonsense. Quite why a distinguished philosophy would do that is beyond me.

Of course, I may be misunderstanding him, but it is hard to see how he get rationalise low P(R/N&E) otherwise.

4. Plantinga seems to confuse beliefs with instinct. Evolution does not give is beliefs, it gives as the faculties to create true beliefs most of the time. Many prey animals feign death as a strategy to avoid getting eaten - playing possum. This is instinct, something they do automatically without thought, and in hard-wired into their brains. This is the product of evolution.

Belief is something different. Evolution has given us the tools to create beliefs, not the beliefs themselves. An individual one sees someone mauled by a beast with claws and teeth and concludes that all beasts with claws and teeth should be evaded is at an advantage, especially compared to the guy who concludes the appearance of a tiger signifies the start of a race.

And to me, this seems trivially true. It is so obvious I have difficulty understanding how Plantinga is failing to see this.

The flaws here seem quite clear to me, and I have to wonder about Plantinga. Even if I have misunderstood him, it is bizarre that he does not address any of these issues in his article. Is this another case of a brilliant man blinded by his religion, like John Lennox?