A] God created the world.
B] A combination of random mutation and natural selection gives rise to new species.
There seems to be a persistent assumption that A implies not B. Even worse, there is a minor industry based on the false corollary that B implies not A, which really has no logical basis at all. This annoys me, because a lot of energy is being expended on debates which are logically stupid, but which also have harmful effects.
A is of course commonly known as creationism, and B is commonly referred to as the theory of evolution. I would argue that the two statements are almost independent. Without violating logic, a person could easily assent to both statements, or hold that both statements are false, as well as the more typical configuration of assenting to A and not B (the stereotypical fundamentalist Christian creationist), or not A and B (the stereotypical strictly materialist atheist).
Consider, for example, a Buddhist who does not believe statement A, because he holds that the world has always existed, and that there is no supreme being who could reasonably described by the English word God. I don't think we can predict anything about what this person believes about whether or not new species evolve by mutation and natural selection. Consider also a positivist materialist type who is absolutely convinced that no such thing as a deity could possibly exist (not A). There is no reason to assume that this person believes in Darwinian evolution (B); she could for example be a strict neutralist, who believes that the persistence of some variants in a population is totally stochastic and natural selection has no significant effect. As for someone who assents to both A and B, I don't have to make up an example; I myself hold both statements to be true (though my attitude towards the two statements is not at all identical).
Clearly the root of the problem is not in fact poor logic, it's the existence of a very vocal group of people who say that they believe A, when in fact they also believe α, namely that the creation account in the book of Genesis is "literally" true. α can reasonably be said to imply not B, because if all the species were there at the moment of creation, then there is no speciation and no evolution. In fact, it's not totally unreasonable to say that α and B are fully mutually exclusive; B doesn't strictly imply not α (because Genesis could be literally true, but the standard interpretation of its literal truth could be wrong), but it's close enough.
The people who are putting serious effort into convincing everybody of α and not B are, I believe, rather dangerous. Let's call them political Creationists (to distinguish them from the much larger group of everybody in the world who believes A; that distinction is going to be important for the development of this argument). I don't think that ultimately, political Creationists really care whether the account in Genesis is literally true. The originators of this philosophy are American fundamentalist Christians, and they have two rather unsavoury aims. The first is to force their brand of Christianity into a position of direct political influence, including in public schools. That means they're working to undermine the US Constitution whose First Amendment prohibits establishment of any religion. In one way that's kind of a local issue, but American politics does tend to spill over into the rest of the world.
The second aim is to undermine the credibility of science in general. In order to increase the powerbase of a fundamentalist religion, political Creationists are trying to make critical thinking more difficult. That's what makes it really scary for those of us who are not Americans. It also explains why people who are not at all American fundamentalist Christians are getting involved in this, including a growing minority of Muslims and a few rather wacky Jews, as well as some other Christian groups. It seems like these other groups want a slice of the power that fundamentalists in the US are accumulating, and political Creationism looks like a way to achieve that.
It's understandable that people are worried about this phenomenon. But I find there's a big problem with the measures being taken to combat it. I think the people who are writing books and making TV programmes in which they eagerly try to convince people that evolution really does happen, claiming that this shows all religion is false, are actually allowing the unpleasant element to frame the debate. I am not saying that arguing with them gives them legitimacy, exactly, but more that arguing with them on their terms is already giving them a significant advantage, even if their arguments are weaker. (There's also the fact that the militant atheist crowd annoy me because of the lack of logic mentioned at the start of this post; there's no good reason to assume that all people with any religious views at all necessarily believe α, and it's entirely fallacious to claim that evidence in favour of evolution is evidence in favour of atheism.) But more seriously, arguing as if verifying the Darwinian view somehow "proves" that God doesn't exist (B implies not A), is only encouraging people who don't understand or don't find the theory of evolution satisfying towards the theist, creationist view (not B implies A). For one thing the theory of evolution is hard to understand and not at all intuitive. For a second thing, Darwin himself said some things that were wrong, and other evolutionary biologists have also occasionally said wrong things. Nobody sensible is claiming that scientists are infallible. But the way the debate is being framed by the political Creationists, and the way that framing is accepted by the militant atheists, make it tempting to infer that if Darwin was wrong, then fundamentalist Christians must be right.
In order to "win", all the political Creationists need to do is to convince people that there's a legitimate controversy about the theory of evolution. They don't have to convince people that their version of the origins of life is correct, simply that the standard scientific model is "just a theory", and it's a matter of pure personal preference whether you decide to "believe" in evolution or in literal-according-to-the-fundamentalist-i
Let me make a note about the different values of belief for the two statements. A is clearly a statement of religious belief. You can try to challenge it on logical or empirical grounds if you really want to, but you're probably just going to end up annoying the people who hold the belief. I would venture that the vast majority of people who hold religious beliefs do not hold them because they are completely convinced by some practical evidence or some irrefutable logic. They hold the beliefs because they find them emotionally appealing, or perhaps because they come from a community where those beliefs are common currency. That goes for a lot of atheism too, I would argue. People who hold a particular philosophical or religious belief may try to rationalize it by presenting arguments and evidence, but in the end the justification is primarily a way to make them feel better about themselves, it's not the reason for believing a certain way. (My personal opinion is that anyone who claims they can "prove" God's existence is believing in something that isn't God, and anyone who claims they can prove God's non-existence has misunderstood the nature of religion.)
B is a scientific theory. I happen to think the evidence for it is pretty solid at this point, and it does seem to make good predictions about how biology works. Rationalists defending the theory of evolution often make pious (sic) pronouncements about how scientific theory can always be challenged by new evidence or a better interpretation of current evidence. In principle that's true, but really, how many people have personally examined all the evidence in favour of Darwinian evolution and found it satisfactory? I know I haven't, and I'm a professional biologist! So to some extent people believe B as a matter of trust; we believe in the scientific method, with its empiricism, its peer review, its assumption of induction. And we believe in the scientific establishment as people who are true to the principles of the scientific method, and who genuinely are willing to revise their models when new evidence appears. We accept things as being true because scientists have come to a consensus on them, which is essentially an argument from authority, when it comes down to it.
Now, I do happen to think that science is about the best method we have of understanding the world. But I also think that we shouldn't go too far in assuming that "Science" has access to the Ultimate Truth, and we shouldn't lose sight of the fact that there is an element of trust and assumptions involved. This situation also implies that scientists have a responsibility to communicate their results clearly and honestly to the non-scientific world, and people who are not scientists have a responsibility to be educated enough to maintain a reasonable level of skepticism.
Anyway, the main conclusion is that statements A and B are independent because they are different kinds of statements. If people want to argue for or against one, they shouldn't muddy the waters by trying to talk about the other. The secondary conclusion is that there are some extremely unpleasant people who have a vested interest in convincing people of not B, and that decent people should be very careful in how they argue against such unpleasant elements, to avoid accidentally playing to their hidden aims.
I have other things to say about this topic but this is insanely long anyway. It's prompted by various conversations on the topic, both around LJ and in person. So thanks to smhwpf, pw201, pseudomonas, rysmiel and anybody else I might have forgotten who's been going over this stuff with me. See also, if you're not exhausted by now!
And, er, sorry about the music choice...