Irrationality and Compartmentalization
Over at Pharyngula, in the comments to this post, there's a debate about whether holding religious beliefs impairs the ability of scientists to do good scientific work. Some say no, that scientists, like others, can compartmentalize their beliefs, so that while they may hold irrational religious beliefs they still are rigorous in their scientific work.
Empirically, I would say this is true. There have certainly been some theists and religious believers who have produced excellent scientific work without their irrational beliefs tainting it. The evidence is there.
However, the fact that some people can and have been good scientists despite the cognitive dissonance of working in a rational field and holding irration beliefs doesn't mean that it is a good idea. Because, logically, once a person believes one thing despite a complete lack of evidence, there is no rational basis on which to reject others. That is not to say that they don't; many people cling to their irrational beliefs while (correctly) pointing out the flaws in others'. However, while having one irrational belief does not always lead to others, I would contend that it often does. Once a person rational filters have been breached, even if they haven't been completely disabled, it will be easier for others to get through.
An anectodal example: I knew a guy who used to be, if not an atheist, definitely highly skeptical of religious faith. He once even mocked C.S. Lewis' arguments in Mere Christianity during a discussion with me. Then, after he screwed up his life but good, he suddenly found God.
(Aside: my personal opinion is that since he'd done something pretty bad, he felt like he needed a supernatural man in the sky to "forgive" him and thus relieve him of the guilt he rightly felt for what he had done. But I hate it when Christians try tell me why I'm an atheist -- they always frame it in terms of their belief structure and are always wrong -- so I will give him the benefit of the doubt that I don't actually know why he found Jesus right then).
Now, I'd found him to be fairly rational on most issues up to then. But, after he found Jesus, his entire outlook on many subjects changed. For instance, he'd never once said a word about homosexuals to me until after his conversion, but then, suddenly, he was against equal rights for gays and against gay marriage. When I asked him why, he said, "I don't know. I don't have a good reason, I guess, but I'm still against it."
Now, you might say this part and parcel of accepting Christianity, and thus isn't a separate irrational belief but part of the same one. But no, I disagree. Because it wasn't his sudden opposition to gays and gay marriage that was a new, additional irrational belief. Heck, for all I know, he always felt queasy about the gays and always, somewhere, wished they would go away. I don't know because we never talked about it prior to his conversion. No, what I think is the additional irrational belief that penetrated his rational filter is the idea that "Because I don't like it, it must be wrong, and therefore should be illegal." He had never expressed such a sentiment before his conversion.
I know that I am making a "Slippery Slope" argument here. Of course, despite what you may have heard, the slippery slope isn't always a logical fallacy. But I don't think I am making a slippery slope argument, because I'm not saying that having one irrational belief inevitably leads to others, just that it makes it easier. Not because people consciously think, "Well, I believe this crazy thing, I might as well believe a bunch of others." Obviously, few people believe that their irrational beliefs are irrational (which is the topic for another post sometime). But, I contend, that accepting one irrational belief makes it harder to recognize and reject others. Because whatever false logic one used to accept the first irrational belief probably applies to others, and so once one irrational belief looks rational to you, others can too.
So, while there are good scientists who are also theists, I'd bet that being a theist has rarely helped someone be a better scientist, while I guarantee that it has made a lot of people bad scientists. (William Dembski, just off the top of my head). Over at Pharyngula they're arguing over the wrong question. They're asking whether being a scientist is compatible with being a theist. Clearly, they're not incompatible, so strictly the answer is yes. But the real question is whether being a theist is more likely to improve one's work or detract from it, and I would say, firmly that is much more likely to detract. Ergo, while mixing science and theism isn't impossible, it's just not a good idea.