Is it irrational to think Plantinga is rational?

February 17, 2014

I’m hardly the first to respond to the Plantinga interview.

A few caveats: interviews are a terrible basis to judge a thinker or line of argument. The compression alone means that things are going to look enthymeic at best esp if you are unfamiliar with the work or hostile to the conclusions. Both if these are true for me wrt Plantinga, so my title is perhaps unfair.

OTOH, he put it out there and the title there is equi-offensive/silly so why not?!

I want to address two parts, one in a general way and one in specific detail.

To the first, I think any sort of supernatural being is necessary to fill explanatory gaps has to deal with the fact that every supernatural explanation to date has failed miserably. Our successful predictions and manipulations of the world have come entirely from naturalistic science. And it’s not even close. Given the failures to date, there should be a strong presumption against supernatural explanations going forward.

And note that if it doesn’t give us predictions or manipulations, then we really have to ask whether it is a explanation at all.

Until some reason for thinking this time is different is forthcoming, I think fine tuning arguments should be regarded as nonsense.

Second, let’s look at the cognitive suicide argument. (It actually relates to the above argument.)

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 neurophysiological properties. If it’s also true, that’s fine; but if false, that’s equally fine.

There are two immediate oddities: 1) why worry about true content rather than content at all and 2) why are true and false content equally fine?

The first point suggests that the argument proves too much, or, at least, one might wonder why we are focusing on true content when content itself is threatened.

The second point, I think is based on our belief content being closed under negation (in principle) and bivalence. If P is false then not P is true and, in some sense, the fact that I got a belief that P instead of that not P was a coin flip. Or maybe given bivalence, half of all possible beliefs are false (since half of all propositions are false) and since selection doesn’t select for truth (indeed, it seems that selection is wildly indifferent to truth) we are in no better position with respect to our beliefs than a uniform sampling of content. (Probably within size limits…although, why even that? If content is unmoored from its material instantiation then why can’t we have actually infinite content! I hope it’s clear from such considerations how bonkers this line is!)

But now we’re just into brute skepticism aren’t we? If naturalism and evolution require the idea that content is completely unmoored from our evolution and material basis, then why assume we aren’t zombies (ok, we perceive that we aren’t….but <i>how do we know?!?!?</i>) or generally quite wrong?

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.

Again, why does it produce an equal likelihood? If I select sentences for an arbitrary non-truth tracking property, how likely am I to end up with roughly half of the sentences being true (even given an underlying distribution of half true/half false)? Well, consider the property of “sounding like it was something written by Shakespeare”. My guess is that Shakespeare wrote a lot more affirmative sentences than denying sentences so I doubt we’re going to get an equal number of negated and un-negated sentences. So, I don’t see that we’re going to end up with sets that are half P and half not P. Indeed, given that a big chunk of folks he wrote about are fictional, it seems regardless, I’m going to end up with false sentences. (It’s really a big deal, as Pigliucci emphasises, that the example specifies independent beliefs and defines reliability as “being 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.

Ok, I keep screwing this up (e.g., on FaceBook). It’s true that if getting true beliefs is like getting heads by flipping a fair coin, that the probability of getting 67 out of 100 (or even 67 or more out of 100) is very low. Of course, the probability of us getting very few beliefs being true (say, 33 or less) is also wildly improbable. But, so exactly what? Let us even grant the skepticism, i.e., that for any given belief (knowing nothing else about it!) it’s as likely to be true as false. This doesn’t tell us anything about whether we are, indeed, in that situation. In fact, there’s plenty of reason to think that we are in that situation! (Consider John Ioannidis’ famous paper, “Why Most Published Research Findings Are False“.)

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.

Given that we know lots of our faculties and belief forming processes are wildly unreliable, why is believing that a fall into total skepticism? The not entirely hidden premise is that our belief forming processes are reliable in this way (i.e., generate far more truths than falsities). But is that true? Can it not be true without total skepticism? Well, I don’t feel like a total skeptic, and I’m pretty convinced by Ioannidis. Of course, a key features of Ioannidis is having a more sophisticated analysis of belief such that beliefs are not all of a piece. Within naturalistic science, evolution and materialism have tremendous weight of evidence. Essentially, all the evidence points that way at every level. And we can distinguish between people who are essentially indifferent to evidence and those who are not. Astrologers do a crappy job of making concrete predictions. Creationists have produced no scientific discoveries. Etc. etc. Theologians have made predictions about the world (and the sort of explanation we will find) and have been wrong, wrong, and wrong again. Why would this metaconsideration make us feel otherwise? Isn’t more likely, ex ante, to be wrong, yet again?

(This needs tightening. Grr.)

(Update: PZ Myers has, I think, a similar set of considerations. Unsurprisingly, he’s not as charitable to Plantinga’s argument. But the core bit is similar: Our brains and senses are unreliable! That’s why we put so much effort into knowing! This doesn’t defeat Plantinga’s argument in detail, but one does have to wonder why we need to do that.)

About these ads

One Response to “Is it irrational to think Plantinga is rational?”


  1. […] A propósito do teísmo, duas respostas breves, mas dignas às estranhíssimas declarações dadas por Alvin Plantinga nessa entrevista: aqui e aqui. Até meu amigo Bijan Parsia fez alguns comentários. […]


Comments are closed.

Follow

Get every new post delivered to your Inbox.

%d bloggers like this: