Getting philosophical, getting committed.

There's something about the ongoing evolution versus intelligent fisticuffs that's been festering with me. It's one of the criticisms that's been leveled at evolutionary theory by folks like Phillip Johnson: the claim that evolution is a philosophical theory. Here's the claim, in context, as presented by a student newspaper at the University of New Mexico covering a talk Johnson gave there:

Johnson said the theory of evolution, or any theories like it, will not survive the 21st century because evolution is a philosophical theory.

He went on to say that one of the major flaws of the theory of evolution is that it excludes the possibility of divine intervention within the creation of living organisms.

“What we have is a theory that supports a moral view that nature is all there is and God is completely out of the picture,” Johnson said.

He said that one of the reasons God is left out of the theory is because scientists are either atheists or very liberal about religion.

Johnson’s speech concluded on the proposal that students should be taught a variety of theories regarding the way life is started — not just evolution.

Now, I know there's a long history of trash-talking various moments in the history of science by saying they look more like philosophy than science. Thomas Kuhn noted that a sure sign that your paradigm is in trouble is that the discussion gets philosophical. He wrote:

It is, I think, particularly in periods of acknowledged crisis that scientists have turned to philosophical analysis as a device for unlocking the riddles of their field. Scientists have not generally needed or wanted to be philosophers. Indeed, normal science usually holds creative philosophy at arm's length, and probably for good reasons. (Structure of Scientific Revolutions, p. 88)

Closer to home, I know what it's like to call one's mother and tell her her child is leaving a perfectly reputable scientific field to become a philosopher. I get that dropping the phi-bomb on a scientific theory is intended to damage reputations and hurt feelings.

But can we pull back for a moment to look at what the content of the slur is supposed to be?

PZ Myers responds (in part) to Johnson and his posse of trash-talkers this way:

You could also claim that Christianity, capitalism, and democracy are "philosophical theories"—that doesn't imply at all that they are going to expire. Evolution is not speculation and faith and guesswork, there is evidence…and what evolution tries to do is explain the evidence.

While I'm grateful for the assurance that philosophical theories aren't about to be yanked off the shelf like expired milk, PZ is gesturing towards a line one should draw that separates evolutionary theory from "philosophical theories" like Christianity, capitalism, and democracy. Johnson seems to be recognizing the same line, but disagreeing about what side evolutionary theory is on. PZ suggests that the "philosophical" side is where you'll find the theories based on speculation, faith, and guesswork. Johnson (as portrayed in the linked article -- even given his track record, I'm hesitant, given experiences with the school paper here, to assume the student paper at UNM necessarily got it right) seems to be saying "philosophical theories" are the ones that use their metaphysical commitments to support certain moral views and undermine others.

So, is the ideal supposed to be that scientific theories are utterly and completely free of philosophy? May I gently remind my scientific friends that, in the medieval university, we'd all be in the same department (or at least, on the same hall)?

Of course scientific theories bring some philosophy with them. You think the data we collect today can help us make good predictions about what will happen tomorrow? That reflects a metaphysical commitment you have about what kind of universe you're living in. And there's nothing wrong with having that commitment. Indeed, it's what helps some of us get out of bed in the morning. You want to show me the analysis that shows your results are statistically significant? Fine, but don't forget that the claim of statistical significance rests on metaphysical commitments about the normal distribution of data in the bit of the world you're studying. If you didn't start with some metaphysical hunches, there would be no way to do any science.

But, clearly, there is a difference between doing this and jumping into a "philosophical theory" of the sort Johnson and PZ seem to have in mind. And here, let me be the millionth person to point out that there is an important distinction between what one takes up as a methodological strategy and what one takes on as a metaphysical commitment. To Johnson, the fact that God is not mentioned anywhere in evolutionary theory is equivalent to biologists saying they're committed to the non-existence of God. To biologists, on the other hand, the non-mention of God reflects a methodological commitment to explain phenomena in the natural world by pointing to natural causes. Saying, "I'm only going to accept causes of types X, Y, and Z in explanations of this sort of phenomena" is not the same as saying, "There's nothing there but causes of types X, Y, and Z." If, as I pour a flask of water on a spoonful of table salt, I dance the tarantella, it would be silly to accuse the chemist, who explains why the salt dissolved by pointing to the structure of the salt and the structure of the water, of denying the existence of the tarantella. Clearly, the tarantella exists, but the chemist doesn't need it to explain why the salt dissolved.

(Occam's razor? Also philosophical. Don't let it freak you out.)

The deal with science — the thing that makes it different from some "philosophical theories" you might worry about — it that there's a serious attempt to do the job of describing, explaining, and manipulating the universe with a relatively lean set of metaphysical commitments, and to keep many of the commitments methodological. If you're in the business of using information from the observables, there are many junctures where the evidence is not going to tell you for certain whether P is true or not-P is true. There has to be a sensible way to deal with, or to bracket, the question of P so that science doesn't grind to a halt while you wait around for more evidence. Encounter a phenomenon that you're not sure is explainable in terms of any of the theories or data you have at the ready? You can respond by throwing your hands up and hypothesizing, "A wizard did it!" , or you can dig in and see whether further investigation of the phenomenon will yield an explanation. Sometimes it does, and sometimes it doesn't. In cases where it does not, science is still driven by a commitment to build an explanation in terms of stuff in the natural world, despite the fact that we may have to reframe our understanding of that natural world in fairly significant ways.

So really, philosophy is not the problem here. Rather, the problem is hanging certain metaphysical commitments on science that are extraneous to the job it's doing.

Which commitments are separable from which others, and which commitments are joined at the hip, can be a tricky business if you're not used to thinking carefully. (See, for example, the current debate over whether you can support disability rights and also support physician assisted suicide.) Even people who think for a living can let their assumptions go unquestioned if they've been humming along for a while. But, it seems to me, if you want to know what a scientific theory commits you to, you might want to talk to some scientists who use the theory. If you're really brave, you could even ask a philosopher of science.


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