Politics and religion sometimes make people say stupid things. They even sometimes make otherwise quite intelligent people say stupid things. Perhaps it’s naive, but it does seem natural enough to expect that unusually intelligent people would have intelligent things to say about things in general, and that they wouldn’t suddenly start sounding like people of merely average or lower intelligence when the conversation turns to religion or politics. This expectation seems to be satisfied insofar as the people who most often have intelligent things to say about politics and religion are, well, otherwise pretty intelligent. But it continues to astound me how often really smart people seem to lose hold of their intellects when they think there might be something at stake. I suspect that anyone with a Facebook account has encountered this phenomenon. I have encountered it enough times today that I feel compelled to write about it.

Today’s most egregious offense appeared in a Facebook post complaining about the teaching of ‘intelligent design’ in schools. In case you’ve been living under a rock, ‘intelligent design’ is the label for a loosely related set of theories that criticize Darwinian evolutionary theory and purport to offer an alternative scientific hypothesis about the origin and development of life: life is (surprise!) the product of intelligent design. This family of theories is widely dismissed by scientists and usually endorsed only by religious believers (and not even by many of the most educated and informed religious believers, at that). The controversy that has occasionally boiled up in the United States over whether it should or should not be taught in schools owes much of its heat to its apparent religious implications and motivations; critics charge not only that it is bad science, but that it is a not very covert attempt to inject religious dogma into science classrooms and public education more generally. I’d thought that the political debate about this issue had more or less died a while back, but apparently not, since I found myself this morning reading a rather strong condemnation of efforts to teach intelligent design.

As it happens, I entirely agree with the author of the condemnation that intelligent design should not be part of any school’s science curriculum. I’m not sure whether it’s all quite so intellectually bankrupt as its fiercest critics say, but it seems clear enough that it’s not science; if it belongs in a curriculum somewhere as anything aside from a historical or cultural curiosity, it’s in a philosophy class, not a biology class (unless it’s an unusually philosophical biology class). But the particular post I read today did not content itself with rehearsing the many reasons in support of this verdict. It went on to claim that the whole line of reasoning involved in intelligent design theory, the impulse to what its proponents call ‘the design inference,’ is intellectually lazy; inferring that something has been intelligently designed is just akin to giving up the search for a real explanation. This might have been forgivable, the thought seems to go, in an age before science, when otherwise great thinkers simply lacked the resources to envision any plausible alternatives, but we know better now, or ought to, and ‘the design inference’ should be recognized for the surrender of rationality that it is.

This line of argument gets whatever plausibility it has, I suspect, from a tacit restriction of the cases to which it’s supposed to apply. After all, most of us who have spent much time conversing with creationists have no trouble remembering people we’ve met who really couldn’t see how the eye, say, could have evolved entirely apart from the agency of some intelligent being, and, well, there’s a quite rich body of scientific theory about the evolution of the eye that succeeds at least in identifying a plausible explanatory account of how eyes evolved — and, as it turns out, evolved independently many times. So there really do seem to be cases in which ‘the design inference’ exhibits intellectual laziness. There are many others, however, in which it is not lazy at all, and is in fact reasonable and indispensable.

If that seems like a strong claim, it’s because you’re only thinking about biology. You should instead be thinking about archaeology. One of the things that archaeologists routinely do is identify certain material remains as artifacts. They dig some stuff up out of the ground and infer in some cases that the items in question were made by people who intentionally crafted them for some purpose or other. Sometimes archaeologists can’t agree about what that purpose was, but they nonetheless agree that they’re dealing with an artifact and not some chunk of materials that formed solely through some natural process unguided by any intentions or purposes. In other words, archaeologists routinely make the design inference. I’m not an archaeologist, so I don’t know, but I imagine it’s often a pretty easy inference. Its ease doesn’t make it lazy, though, and certainly doesn’t warrant the judgment that it is an alternative to ‘real’ explanation. No doubt there are deeper, fuller explanatory accounts to be given of the formation of human artifacts, of what’s going on when a human being intentionally creates an object for some purpose. But those accounts aren’t going to eliminate the difference between an artifact and, say, a natural rock formation. Unless archaeology is a pseudo-science, the design inference is not merely a lazy alternative to genuine explanation.

But perhaps I’m being uncharitable to the author of this complaint; maybe the complaint is supposed to apply only in the realm of biology. Here too, though, it seems pretty silly to regard inferences to design as mere laziness. Set aside the possibility that genetic engineering and other sorts of biotechnology render some biological phenomena the products of intelligent design. Even when we’re thinking only of phenomena that we can be reasonably confident aren’t the products of intelligent design, we shouldn’t forget that non-teleological evolutionary explanations are deeply counter-intuitive. There’s a reason why such explanations have come to be widely accepted only relatively recently in the history of science despite the fact that the basic idea had already been formulated by Epicurus and, before him, by Democritus and (in a slightly weirder form) Empedocles. It took a whole lot of empirical observation and sophisticated theorizing before the idea of evolution by natural selection could reasonably be regarded as a viable scientific theory, let alone as indispensable to biology. No doubt some folks have a difficult time thinking their way out of what they’ve been taught to believe all their lives, and perhaps for them there is really nothing counter-intuitive about evolutionary theory. But in fact it cuts against the intuitions that most human beings in most times and places have had. This is not a strike against it. Rather, it illustrates something important about science and about rational inquiry more generally: sometimes the most reasonable theory available really does run contrary to strong, widely shared intuitions. The moral of the story ought not to be that those intuitions are lazy and stupid, but that successful intellectual inquiry is often hard. To castigate design inferences, even in biology, as mere laziness is akin to chiding someone as lazy just because he can’t run a marathon.

Of course, to many people, accepting biological explanations that appeal to natural selection will hardly seem like the intellectual equivalent of running a marathon. But such acceptance is itself more akin to watching somebody else run a marathon. It’s pretty uncool to tell people who can’t run marathons that they’re lazy. It’s even more uncool to sit on your ass watching other people run marathons and then tell people who can’t run marathons that they’re lazy. The fact is that most of us who believe in evolution — even most who can generate a roughly accurate description of the theory, a group that turns out to be rather smaller, in my experience, than the group of those who believe it — don’t believe it because we took a long, hard look at all the evidence, carefully considered the theory, and concluded that it’s the most satisfying explanation around. Most of us aren’t even competent to assess the evidence adequately. Virtually all of us instead believe the theory on authority. Not blind authority, and not unqualified authority, but authority. We didn’t do the hard work of assessing the theory in the way that genuine experts do, let alone formulate it for ourselves. If we see nothing counter-intuitive in it at all, chances are it’s because we’ve never been able to think our way out of our own prejudices. This is one thing, at least, that reading old books by smart people can do for us.

So I’m not defending ‘intelligent design’ in the least here. There are, as I am dimly aware, plenty of interesting scientific and philosophical problems and perplexities about the origin and development of life, but so-called intelligent design theorists don’t have much to contribute to understanding them, and until intelligent design theorists manage to generate empirically informative research projects that make some kind of positive contribution to biology, their ideas won’t have any real place in science classrooms. But it is foolish to allow political and religious antipathy towards intelligent design theorists to lead us to make ludicrous claims about the rationality of inferences to design or to overlook one of the most interesting and exciting things about science, which is exactly its tendency to surprise us, to lead us to conclusions that we wouldn’t have expected, to show that what is otherwise counter-intuitive and subjectively improbable is in all likelihood actually true.

So why do otherwise intelligent people allow ideology to lead them to say stupid things? I could conjecture that it’s just intellectual laziness, and there may be something to that. But it sure happens an awful lot, and not only to people who are usually intellectually lazy. I suspect that we get more informative explanations from the likes of Daniel Kahneman and Jonathan Haidt; in any case, a genuinely informative explanation will have to come from some psychologist somewhere, and not from me in my armchair. I wish I could conclude this diatribe with a self-righteous exhortation to the intelligent among you to shun this particular vice, but I know from experience that I’m not immune to it myself, so I’ll try to focus on keeping my own eye free of planks before I indulge in any more speck removal operations. I’ve never been especially successful at exhortation anyway.

So instead, for your delectation, a really counter-intuitive but ultimately plausible and very probably true story about the evolution of the eye: