Darwin's 200th. Yay! The series of articles about him in science magazines has been extremely interesting - lots of things that I didn't know.
It's a great day to remind people, also, of why we believe in evolution. For the most part, it's because we've been told to - belief in evolution is almost entirely a matter of deference to the authority of the scientific establishment. I would wager that not one of you could produce primary evidence that demonstrates that evolution by natural selection actually happened. Sure, you can point to journal articles, and pictures in books. Have you personally seen the hip-bones of a whale? Have you personally performed phylogenetic analysis on DNA sequences? Even if you did - as I have - can you be sure that belief in evolution did not entail the contents of the sequences themselves? Ascertainment bias creeps in everywhere! How do you know it's not all a big house of cards? The answer is that you don't: you merely trust that these things are true, and you do so because other people say they are.
It is fortunate that most people I know defer to the authority of science. Because, as authorities go, it's really quite good, and well worth supporting. Deference to science has supported our household very well. Like everyone else, we believe whatever we are rewarded for believing, and the rewards for believing in modern biology are rich indeed. But I don't make the mistake of attributing this belief to "intelligence" or "rationality". That's just a gloss people put over their faith in order to make it seem more respectable. Belief in evolution is fundamentally a political decision, and the reason it is political rather than rational is because we encounter it not through interaction with the natural world, but through the words of other people.
Others have a very different experience with science; they are alienated, and sometimes oppressed by it. The church, on the other hand, rewards some people quite lavishly for their deference to scripture. I know several people who have been literally pulled out of the gutter by fundamentalist faiths. This makes me shudder, to be sure, but I can't deny that the church has a hell of a lot more authority in their lives than some white-suited geek that spouts unintelligible jargon at them. How could it be otherwise?
The past does not exist. It is gone. It has no more claim to reality than the future. However, we can construct models of the past that have enough fidelity to allow us to not only suspend disbelief, but to influence events in the future in ways that we find agreeable.
When postmodernists moan that science is "just a social construction", I can't argue with that, but I do wonder about the meaning of the ever-present word "just". That's like saying your house is "just" the work of a carpenter - as if you expect your home to be some sort of natural object that springs out of the ground on its own. Pity that it isn't, because then it would be something you could take for granted, something you wouldn't have to worry about. Something unimportant. Once you realize that it's constructed, you realize that it requires maintenance and repair, that what is constructed is easily un-constructed and rendered useless. Your home, by being a construction, must be defended if it's to keep the rain off your head.
So it is with science. We justify belief in science because we can see that multiple lines of evidence point to consistent conclusions. This "evidence" doesn't consist of observations of the natural world, but rather, it's overwhelmingly built from observations of copies of texts we believe were written by people who observed the natural world, and who in turn serve as the subjects of copies of other things written by the people who observe the people observing the natural world. Sometimes, we can use these texts to accomplish interesting things ourselves, and when they work as planned (which any science student knows is not always the case), we are reassured that this system of knowledge that holds the world at such a distance is more than just words on a page.
Consider something a little less controversial: the atom. We don't just believe that atoms exist because we observe stoichiometric relations in chemistry, or because we can run electricity through gases and predict the color with which they will glow. We believe in atoms because a single theory yields precise predictions about multiple unrelated results in different situations. [And we must include in this theory the whole system of publication and peer review that brought it to us in the first place.] Atoms are considered "real" because this belief is parsimonious. And that parsimony is in no way diminished by a system of mutually interlocking theories that describe, among other things, the apparatus used to make the measurements that support the theory itself. Are atoms really "out there" in the way tables and chairs are? Maybe. Maybe not. But the theory is not a "house of cards" - it is a strong, solidly built house that has withstood everything that has been thrown at it. A well constructed house. There is no "just" about it; social construction is the whole point.
In thanking Darwin for the fine theory he has presented us with - a theory of the unseen past - we should thank him for being not just a good scientist, but for being an even better politician. And we should believe in evolution not because it is true in some objective sense, but because it is so useful for achieving the things we want to achieve, none of which can be accomplished outside of the social and political systems that created it. And finally, we should not casually dismiss the creationists, for one simple reason: There but for the grace of the angels go I.
Instead, we should respect creationism for being yet another socially-constructed paradigm in the multiverse of human rationality. Then we should crush it, and destroy its supporters, because insofar as our socially-constructed world of science can never be taken for granted, they are a threat to civilization itself.
