November 4, 2009

Over at Ex-apologist’s blog, the former apologist links to a paper and a response to it which straddle the boundary between physics and theology. I’m a sucker for this sort of stuff. The paper is J. Brian Pitts’s Why the Big Bang Singularity Does Not Help the Kalam Cosmological Argument for Theism, and the response comes from William Lane Craig, who revitalised the Kalam argument for the existence of God.

There are some real physicists reading this, so I’d be interested to know what you think of this stuff. I’ve left a comment over on the ex-apologist’s blog, which I’ve pasted below:

I love this stuff: it combines physics, philosophy and religion. I don’t think Craig’s response addresses Pitts’s paper terribly well: they appear to be talking past each other. I have a physics degree gathering dust and a passing acquaintance with the philosophy of science, and I don’t find Craig terribly convincing (but then, I’m also an ex-Christian atheist, so I wouldn’t, would I?)

Craig seems to have misunderstood Pitts. Craig says the Kalam does not rely on a singularity but merely on the universe having a finite age, but as a matter of fact, Craig does appear to argue that the Big Bang singularity represent divine intervention, so Pitts’s Cosmic Destroyer argument seems to have some force. When Pitts makes this argument, he accepts, for the sake of the argument, Craig’s own claim that the past singularity of the Big Bang represents God’s creative intervention, and asks why someone who accepts that claim would not also say that God intervenes destructively in black holes. The idea that God would do so probably seems silly to Christians, but Pitts says that on Craig’s own argument, this feeling of silliness isn’t well motivated. On the other hand, if the feeling of silliness is correct, perhaps Craig is wrong about singularities. A third possibility is for Craig to find some way to distinguish between the singularities, but Craig does not address this directly in his response.

Pitts’s thoughts about possible other theories aren’t necessarily an expression of Pitts’s theological commitments (whatever those may be). The reference to van Fraassen is a clue (and the fact that this stuff is published in a philosophy of science journal): Pitts is talking about the arguments between scientific realism and more empiricist philosophies of science which owe something to logical positivism, such as van Fraassen’s own constructive empiricism. He’s taking a middle position: the unobservable objects posited by theories are meaningful but we ought to be careful about how far we believe they are real (van Fraassen says we can have no grounds to do so, though, contra positivism, we can accept that our theories meaningfully make such claims about unobservables; realists say there are grounds for believing in unobservables). Craig appears to be quite a bit more of a realist about General Relativity than Pitts, or indeed than working physicists like Sean Carroll.

The references to Bach-Weyl and so on are waved away (I’m no expert, but I think in that specific case, rightly, since as far as I can tell Pitts is talking about an early, failed attempt at a unified theory of gravity and electromagnetism), but the possibility of a theory which does not give lengths (durations) to curves should worry Craig, unless he is completely committed to GR. What does it mean to say “the Universe began to exist” on such a theory, or if the universe looks like Carroll thinks it does? Dennett: “What Professor Craig does, brilliantly and with a wonderful enthusiasm, is he takes our everyday intuitions—our gut feelings about what’s plausible, what’s counterintuitive, what couldn’t possibly be true—and he cantilevers them out into territory where they’ve never been tested, in cosmology where whatever the truth is, it’s mindboggling.” (thanks to Daniel Fincke for that one).