by Greg Krehbiel on 17 December 2011
As you may know, Alvin Plantinga is a well-known Christian philosopher who recently wrote Where the Conflict Really Lies: Science, Religion, and Naturalism. There’s a short interview with Plantinga here, which is somewhat interesting.
Plantinga defends an argument that I first encountered through C.S. Lewis, many years ago. In brief, it goes like this. If your mind is a product of your brain, and your brain is a product of random natural selection, you have no grounds to trust it.
The argument is much more detailed than anything I’m going to say here, but by way of simple summary …
… if this is true, if our minds are aimed at mere survival, not at truth, then it’s not probable that our minds should be reliable….
Plantinga points out (rightly, I think) that you wouldn’t expect unguided evolution to produce a brain that is a reliable arbiter of truth.
But “not expecting it” is not the same as “this can’t happen.”
As I’ve thought through some of this it seems to me that we have two versions of this arument — “weak Plantinga” and “strong Plantinga.”
Weak Plantinga might go like this. Naturalism doesn’t explain a brain ordered towards truth. The human brain is ordered towards truth. Therefore naturalism doesn’t explain the human brain.
That seems like a reasonable argument to me, with some caveats I mention below.
Strong Plantinga might go like this. Naturalism can’t explain a brain ordered towards the truth. If a brain is ordered towards truth, naturalism must be false. The human brain is ordered towards truth. Therefore naturalism is false.
That bugs me, because I don’t think you can move from “we wouldn’t expect naturalism to be able to do this” to “naturalism can’t do this, therefore something else is required.”
Another thing that bothers me about this line of argument is that I don’t think we’re dealing with binary choices. Our brains are neither entirely reliable nor entirely unreliable. (Maybe I should just speak for myself?) And I’m not sure it’s fair to say “naturalism leads to an unreliable brain” and “design (or whatever) leads to a reliable brain.”
How do we know, anyway?
Plantinga may cover these objections in his longer treatment of this argument. I have only read some of his essays.
One final thing. As I was reading the Q&A with Plantinga (linked above), I had an odd feeling … like I’d heard this kind of thing somewhere before. And then it struck me that the logic was similar to evolutionary psychology. Something along the lines of “we expect A to lead to B, we see B, therefore A.” But when I tried to elaborate on the connection it kinda fizzled. It’s like when have a genius idea in the shower and can’t remember it when you have pen and paper.
-- 2011-12-17 » Greg Krehbiel