December 16, 2011

Plantinga's evolutionary argument against naturalism

I just finished listening to this (a debate between Alvin Plantinga and Stephen Law on Premier Radio):

...which goes on for about an hour.

Or perhaps I should say drags on for about an hour. I didn't feel like either guy put their best case forward. Perhaps either or both thought that their better arguments were too technical, and they were floundering a bit because they found it difficult to simplify what they wanted to say for a general audience.

For something a bit more concise than the YouTube version, here's the Wikipedia article on the subject: http://en.wikipedia.org/wiki/Evolutionary_argument_against_naturalism

My own summation would be this: Since naturalistic evolution (NE) only selects for survival value, not for "true belief", there's nothing that would require beliefs to be true, as long as outward behavior has a survival benefit. For example you might run every time you see a bear because you believe it's fun to race against bears, not because you're afraid of being killed, but as long as you run, that outward behavior is all NE can select for. NE can't select for or against the internal state of mind (Plantinga calls this "content" ) that goes along with the neurophysiological apparatus that causes you to run.

Plantinga claims that this lack of a necessary correlation between outward behavior and internal thoughts makes those internal thoughts, within the kind of brain NE would produce, unreliable. If individual thoughts are unreliable, complex chains of thoughts must be all the more so unreliable (a conclusion based on ten different thoughts, each with only a 50% chance of being correct, has less than a 0.1% chance of being correct). Since a belief in naturalism is itself a complex conclusion, a person who believes in naturalism should conclude that his own mental faculties are so unreliable that his belief in naturalism itself is highly unreliable.

So (by my interpretation of Plantinga), if you want to trust your own thoughts, you're better off trusting that God designed your mind.

As I see it, this is total bullshit. Interesting and clever bullshit, but bullshit nevertheless.

Anything that you can reasonably call "intelligence" has got to be able to handle complex multi-step processes with a reasonably high degree of reliability. If you're going to allow, for sake of argument, that intelligence can come about through natural evolution (Plantinga does allow for that, even if only because he thinks it leads to a contradiction, but he still does allow for it as an initial premise), then what kind of intelligence would it be, and what kind of survuval advantage could it confer, if was a highly unreliable intelligence?

Could intelligence be highly reliable for matters of survival, but not for philosophical matters? I suppose so, but I see no strong case for assuming that. Clearly one aspect of human intelligence which has aided our survival -- even more, allowed us to flourish -- is the evolution of complex language. It would make perfect sense that a naturally-evolved language capability relies on a naturally-evolved system for complex abstract symbolic reasoning.

It would make very little sense, however, and it would be highly inefficient, for an evolved abstract symbolic processing system to carry the burden of the extra baggage of a lot of extraneous, perhaps even contradictory, "content" (in Plantinga's sense of that word), where you could succesfully negotiate all of the symbolic processing necessary to recognize a bear, visually parse a complex landscape and quickly determine an efficient escape route through that landscape, avoid crashing into trees and tripping over rocks, and all that while performing an extra layer of extraneous symbolic processing which involves seeing a bear as a playmate and seeing running away as a game.

What would be even more unlikely would be for such extraneous and mismatched "content" to be shared among multiple humans. It would cause a great deal of communication difficulty (and potentially life-threatening confusion) if unrelated and unreliable "content" got mixed in with our vocalizations.

Would it even mean anything coherent to suppose that I might run from a bear because I think I'm playing a silly game, but that when I explain to a fellow human being why I'm running from the bear the words, "Because I don't want to get eaten!" come out of my mouth? To imagine "content" that never manifests in any noticeable outward manner is to imagine something so abstract that it might as well be invisible pink unicorns.