But here's the catch. There's a difference between a valid argument and sound argument. This is a valid argument:
- If penguins capable of flying exist, then it is likely that some penguins have flown
- Penguins capable of flying exist
- Therefor it is likely that some penguins have flown
And that's where guys like Craig and Plantinga screw up. They're great at constructing arguments that follow proper form, but a lot of their arguments depend on information that, being philosophers by trade, they're not exactly experts on. Let's take the old Kalam Cosmological Argument:
- Everything that begins to exist has a cause
- The universe began to exist
- Ergo the universe has a cause
There is no reason, within anything we currently understand about the ultimate structure of reality, to think of the existence and persistence and regularity of the universe as things that require external explanation. Indeed, for most scientists, adding on another layer of metaphysical structure in order to purportedly explain these nomological facts is an unnecessary complication.Plantinga's evolutionary argument against naturalism is similarly unsound, because it relies on an erroneous description of evolution. It might be valid by following proper form, but it's still a completely bogus argument.
I was on a forum once, and pointed out that William Lane Craig's writing on physics (which are popularly bandied across the interwebs by would-be apologists), were published for an online-only, unaccredited evangelical degree mill. They weren't vetted by any actual physicists. Stephen Hawking, who Craig's made a habit of criticizing, held the Lucasian Chair of Mathematics at Cambridge for 30 years. Golly, I wonder who knows more about physics?
"But you see," those would-be apologies would reply, "Craig isn't arguing about physics. He's arguing about the philosophical implications of physics." Problem is, before you can wax on about the implications of physics, you have to get your physics right. So when you do something like dismiss the use of imaginary numbers, you're showing that you don't really understand how physics works. Conclusions that you subsequently draw are bound to be fallacious.
To be a good philosopher, you have to yield to experts in a variety of other fields. You can't just toss out information you don't like and formulate arguments based on erroneous premises. That's why Daniel Dennett is really good at philosophy, and guys like Plantinga and Craig suck at it. The good ones, like Dennett, learn from other disciplines and know their limits.