Another round of unholy wars seems to have broken out over the last few days. This particular round (again) focuses on the relationship between atheists and theistic evolutionists. The involved parties have broken into two groups, and I think both are being at least somewhat silly. On one side, we have PZ Myers, Larry Moran, and others. This group believes (among other things) that theistic evolutionists attack and weaken science, although not quite as badly as the out-and-out creationists. On the other, we find Ed Brayton, Pat Hayes, and a few others. This group thinks that theistic evolution is just fine, and that taking a strongly atheistic position risks alienating people, and makes the fight against the anti-evolutionists harder to win. (And, yes, I do realize that there is more to each position than the little bit I just wrote. I'm focusing only on the things that I disagree with.)
The debate is hot at the moment, and seems to be getting hotter. Reading posts from both sides, I've become more and more irritated, because both groups seem to be taking some unreasonable positions. Both groups also seem to be talking past each other to a certain extent. In the spirit of offering a mutually agreeable target to the two groups, I'm going to explain exactly why each is being unreasonable.
Let's start with Team PZ. Both PZ and Larry argue that theistic evolution is an anti-scientific position because theistic evolution allows for the possibility that someone has guided evolution to a specific goal (typically us, although I suppose that a few Diskworldians may take the position of the God of Evolution, and claim that the cockroach is the pinnacle of evolution.) That is a simple position, and it is easy to understand. The problem is that they are attempting to apply this simple position to a wide range of beliefs, many of which are separated by very subtle, but very important differences.
The key difference, and the one that neither PZ nor Larry appears to be taking account of, is this: what physical evidence does the believer expect to find for the belief. More importantly, does the believer believe that there is any theoretically possible physical finding that would contradict that belief? If you want to differentiate between unscientific and anti-scientific beliefs, that is a critically important question.
If there is nothing in the physical world that the believer thinks could ever conceivably contradict the belief, then the belief cannot be contradicted by science. It can't be supported by science, either. It's simply not a question that is amenable to scientific examination. The Catholic doctrine of the transubstantiation is a prime example of this. According to the doctrine, the bread and wine of the Eucharist are transformed into the body and blood of Christ, but retain the form of bread and wine. There is no expectation that a molecule-by-molecule inspection before and after would detect any difference whatsoever. An atheist might find that belief to be silly, or even stupid, but there is absolutely no scientific tool that could be used to show that the belief is wrong. The question of whether or not anything physical happens to the bread can be answered, but the question of whether anything at all happens cannot be - unless "anything at all" is predefined to refer to only the natural world. There are quite a few other Christian beliefs that fall into this category. Original sin, grace, the Immaculate Conception - none of these beliefs makes a statement that is remotely testable against the natural world.
If, on the other hand, there is the possibility that evidence could ever exist that would contradict the belief, then things change. As long as the belief is not contradicted, everyone is uneasily content. If the belief is contradicted, however, then things change. At that point, the believer has only two choices. He or she can accept the judgement of science and reject the religious belief, or reject the judgement of science and continue to hold the religious belief. People who do that take a position that is anti-scientific. The position held by Catholics (and other Christians) that Adam and Eve were two real people, the first two humans, and that there were no other Homo sapiens before them falls into this category. The population genetic evidence alone is enough to demonstrate that there was no population bottleneck that severe in modern humans.
If someone has a religious position that includes unscientific beliefs without also incorporating anti-scientific beliefs, then I don't think it is reasonable to claim that they are attacking or weakening science. They simply believe that there is more to things than the physical world. There are theistic evolutionists who hold beliefs that are anti-scientific, but I expect that there are quite a number who do not. Declaring, as PZ and Larry seem to be, that they are anti-scientific merely because they believe in things that cannot be subjected to scientific investigation is simply unreasonable.
There is also a position that Ed and Pat seem to be advocating which is may be right, but is still unreasonable. I'm speaking here of the argument that people who are vocally and rigidly anti-theistic harm the broader fight against creationism in the classroom. That argument is difficult to objectively evaluate, but it is possible, if not probable, that they are correct. Even if they are, expecting people to take that into account is entirely unreasonable.
Evangelical atheism is not an oxymoron, and it is not unreasonable. If someone sincerely believes that religion is harmful, then they have a moral obligation to speak up. To do anything less would be to allow something that they think hurts people continue, without attempting to do something to change it. Expecting, or even hoping for, silence in such a case means expecting or hoping that someone will compromise their ethical principles for reasons of political expediency. Not only is that an unreasonable expectation, it is a morally wrong expectation. Personally, I'd rather fight alongside someone with the strength of their convictions than someone willing to compromise their convictions in the interests of political expediency - even if I disagree with those convictions.
Two groups seem to be staking out sides here, and I think both of them have staked out positions that include some pretty unreasonable things. I'm confident that this leaves me in a prime position to take fire from at least two different directions, but beyond that I've got no idea where this leaves me.
Postscript: John Wilkins and John Lynch have both also written good posts on the topic. John Lynch has declared himself to be in Ed's camp, but did not take a position on the pragmatic value of being quiet about objections to religion, so I didn't include him on that list. Wilkins didn't claim membership in either camp. Reading their posts, I get the feeling that both are relatively close to my own views. If so, that's good. We can take turns hiding behind each other while dodging the two directions of incoming fire.