Monday, July 12, 2010
Science, Religion And Two Very Silly Claims Often Made By Agnostics
If the people running the atheist bus campaign had asked me, I would have balked at the word 'probably' and pushed for something like, "We Can Be As Sure Of The Non-Existence Of God As We Can Of Anything, So Stop Worrying And Enjoy Your Life." Then they would have pointed out that my version is a lot clunkier than theirs, and that it would be harder to fit on the side of a bus in letters big enough for people to read as it rolled down the street, and I would have said, OK, despite my deep commitment to fallibilism about absolutely everything (and, yes, that includes fallibilism, and no, you can't run a self-refutation argument against fallibilism on that point, unless you want to beg the question by simply assuming that certainty is a requirement for knowledge), I'm slightly uncomfortable with the word "definitely", but I'll accept it as a necessary simplification for the sake of space.
As it happens, Richard Dawkins, being prominently involved in the project, actually did argue for the phrasing "almost certainly." Whether or not this is equivalent to my "as sure as we can be about anything" formulation presumably depends on whether Professor Dawkins thinks that we can be absolutely certain about anything. (I'm not sure.) My position, at any rate, is that (a) the Stone Paradox is just as much of a logical problem for the claim that an omnipotent being exists as Russell's Paradox is for naive set theory, (b) we have powerful empirical evidence against the existence of God in the form of the Problem of Evil, and that, (c) given the total absence of anything resembling evidence for the existence of God, even if there were no evidence against the existence of God, and theism were a logically coherent position, and we were in an "all else being equal" situation, atheism would still win hands down as a matter of sheer ontological simplicity.
(If I tell you that an invisible three-inch-tall elf is jumping around on my right hand as I type, tap-dancing and singing show tunes at a frequency that no human or piece of recording equipment can detect, your response will obviously and correctly be active disbelief. No rational person would respond with, "well, it's probably wiser for us all to be humble and admit that no one really knows whether or not there's an elf....")
Despite all of this, a lot of nice enlightened tolerant liberal agnostic types balk at the claim that we can be confident about the non-existence of God, citing the deeply silly and confused claim that "you can't prove a negative." A related and equally silly objection comes from people who, often in the context of tut-tutting at the involvement of folks like Dawkins in things like the atheist bus campaign, say (often in a tone that indicates that they take themselves to be delivering a great insight) that "there can't be a conflict between science and religion because they concern different subjects."
(Note that, while I have heard one or two people who do philosophy for a living express similar sentiments--even the best of us have days where we haven't had enough coffee in the morning to think straight--I'm mostly talking about "the folk" here, or rather a certain very recognizable subsection of the folk who read the New York Times, listen to National Public Radio and studiously avoid having "extreme" or "strident" opinions about anything.)
The force of that second objection, of course, relies on playing with an ambiguity about the word "science." If by "science", you mean to narrowly refer to chemistry, physics, biology and so on, then, sure, it's true that there's no direct logical conflict between theism itself and the deliverances of these fields. Of course, many religions do make specific claims that can and do conflict with the findings of physics, chemistry, biology and so on--creationism being only the most obvious example--but other religious views are specifically designed to avoid such conflicts, and certainly the claim "an all-powerful, all-knowing, all-good being exists" doesn't by itself directly conflict with the findings of any of those fields.
If, however, by "science", one means to refer more broadly to the overall project of trying to understand the world in a rational, evidence-driven way--with chemistry, physics, biology and the rest being important elements of that project, but not the whole of it--then, yes, "science" in that sense does indeed conflict with religion, in so far as the Problem of Evil gives us an extremely convincing empirical, evidential argument against theism, there's no evidence for the existence of God, and the sorts of considerations of simplicity, non-adhocness and so on that necessarily drive theory selection in every part of the overall project should lead us to favor atheism.
The first objection is even stranger. Of course you can prove a negative. I'm constantly amazed by the number of otherwise bright, college-educated people who have somehow gotten it into their heads that it's impossible to do so. If by "prove," one means "show by means of evidence," then, remember, Sir Karl Popper thought that the whole of science was a matter of disconfirming theories--conjectures and refutations--and never a matter of confirming them. Even if one isn't willing to go quite that far, it's still indisputably true that we often have evidence that shows us that certain things are not the case. If a consequence of Astronomical Theory A is that such-and-such planet will be at such-and-such position at a certain time, and at the relevant time, we observe the relevant position and the planet isn't there, that's evidence against Astronomical Theory A. (Similarly, an obvious consequence of theism is that unnecessary suffering shouldn't exist, but it does exist, in great quantities, and the theist has no convincing way to explain it away. This is evidence against theism.) Without this sort of negative evidence, the process of doing science would be unrecognizable.
(Also, of course, given the logical law of double negation, any evidential confirmation of any claim P is also a confirmation of the negation of ~P.)
If by "proof", one does not mean "demonstration by evidence" but "proof" in the strict sense used by mathematicians or logicians, then the claim that "you can't prove a negative" becomes, if possible, even sillier and stranger than it was when we understood "proof" evidentially. There are simple, elegant and decisive proofs of the fact that there's no largest prime number, that there's no set of all ordinal numbers, and so on. So, whether one means "prove" in this narrow sense or in a broad enough sense to include evidential confirmation, the claim that one can't prove a negative is bizarre.
Still, can we specifically prove this negative (that God doesn't exist), in the strict, narrow sense of "prove" just discussed? I think so, yeah.
One of the most famous negative proofs in the history of philosophy and mathematics is Bertrand Russell's refutation of naive set theory, which goes like this:
Start with the claim that, for every description you can come up with, there's a set of all and only and only the objects that match that description. Question: What about the set of all sets that are not members of themselves? Is it a member of itself? If it is, it isn't, and it isn't, it is. Either way, we've got a contradiction.
Here's the equivalent for God:
Start with the claim that a being exists who can do anything. Question: What about creating a stone so heavy that He Himself cannot lift it? If He can create it, then there's something the being that can do anything can't do (create the stone), and if He can't, then there's something the being that can do anything can't do (lift it). Either way, we've got a contradiction.
"But, wait," you say, "can't we just be more careful and re-define omnipotence to avoid these problems? Let's just say that God can do pretty much anything, but there are some limits imposed by logical possibility."
Sure, you can say that. Similarly, the naive set theorist could respond to Russell's Paradox by being more careful about how to express their unrestricted comprehension axiom. They could just say that for pretty much any description we can come up with, there's a set of all and only the objects that meet the description, but that there are some restrictions on this imposed by logical possibility. Or they could reject one of the logical laws used to derive the contradiction. Or they could pull a Modus Ponens where everyone else opts for Modus Tollens, and take Russell's Paradox as an argument for the existence of true contradictions. (Graham Priest does, in fact, take precisely this line, and people who've read this blog before know that, while I disagree with Priest, I take his argument very seriously.) There's a general lesson here: given a conflict among one's beliefs, there are always many different ways of changing those beliefs to resolve the conflict. The process of rational belief revision is all about carefully weighing the options and choosing the best and most plausible alternative. Considerations of simplicty, non-adhocness and so on will come into play, and no solution can be absolutely ruled out in advance.
....which brings us back to where we started. Can we be absolutely certain that God doesn't exist? Nah. But we can be as sure about that as we can about anything, and the bus-campaigner's adjective "probably" severely understates the case.