Monday, October 26, 2009

Kitcher et al on the fact of evolution

Couple of weeks ago Nicholas Wade had a largely positive review of Dawkins' latest book, The Greatest Show on Earth: The Evidence for Evolution. However, in the second half of the review he accuses Dawkins of mixing up theory with fact when talking about evolution:
There is one point on which I believe Dawkins gets tripped up by his zeal. To refute the creationists, who like to dismiss evolution as “just a theory,” he keeps insisting that evolution is an undeniable fact. A moment’s reflection reveals the problem: We don’t speak of Darwin’s fact of evolution. So is evolution a fact or a theory? On this question Dawkins, to use an English expression, gets his knickers in a twist.
Well...philosophers and biologists have spoken overwhelmingly in defense of Dawkins. Yesterday's NYT published two letters in print and several others online - almost all clarifying Wade's confusion about fact and theory. I will here highlight the one by Philip Kitcher - since he was our Science & Religion speaker last semester - oh and also because he makes his point very clearly:

To the Editor:

In his review of “The Greatest Show on Earth,” Nicholas Wade charges that Richard Dawkins is guilty of a philosophical error. According to Wade, philosophers of science divide scientific propositions into three types — facts, laws and theories — and, contrary to Dawkins’s assertions, evolution, which is plainly a systematic theory, cannot count as a fact. However, contemporary philosophy of science offers a vastly more intricate vocabulary for thinking about the sciences than that presupposed in Wade’s oversimplified taxonomy and in his confused remarks about “absolute truth.” Although philosophers may quarrel with aspects of Dawkins’s arguments on a range of issues, he has a far firmer and more subtle understanding of the philosophical issues than that manifested in Wade’s review.

The crucial point is that, as Dawkins appreciates, the distinction between theory and fact, in philosophical discussions as in everyday speech, can be drawn in two quite distinct ways. On the one hand, theories are conceived as general systems for explanation and prediction, while facts are specific reports about local events and processes. On the other hand, “theory” is used to suggest that there is room for reasonable doubt, whereas “fact” suggests something so amply confirmed by the evidence that it may be accepted without debate.

Opponents of evolution slide from supposing that evolution is a theory, in the first sense, to concluding that it is (only) a theory, in the second. Any such inference is fallacious, in that many systematic approaches to domains of natural phenomena — like the understanding of chemical reactions in terms of atoms and molecules, and the study of heredity in terms of nucleic acids — are so well supported that they count as facts (in the second sense). Many scientists and philosophers who have written about evolution have pointed out that the contemporary theory that descends from Darwin has the same status — it, too, should count as a “fact.” Dawkins is entirely justified in following them.
New York
The writer is the John Dewey professor of philosophy at Columbia University and a former editor in chief of Philosophy of Science, the journal of the Philosophy of Science Association.
In another letter, even Stephen Jay Gould stepped in from the grave to correct Nicholas Wade:
This was most eloquently stated by Stephen Jay Gould, who wrote (in “Evolution as Fact and Theory,” reprinted in “Hen’s Teeth and Horse’s Toes”): “Well, evolution is a theory. It is also a fact. And facts and theories are different things, not rungs in a hierarchy of increasing certainty. Facts are the world’s data. Theories are structures of ideas that explain and interpret facts. Facts do not go away when scientists debate rival theories to explain them. Einstein’s theory of gravitation replaced Newton’s, but apples did not suspend themselves in midair pending the outcome. And humans evolved from apelike ancestors whether they did so by Darwin’s proposed mechanism or by some other, yet to be discovered.”
Read Wade's review here, letters by Daniel Dennett and Philip Kitcher here, and all the remaining letters here. If I'm Nicholas Wade, I'm not getting out of bed for the next few days.


Andrew Shields said...

I was puzzled by Wade's comments, which seemed internally consistent but externally unconvincing, if you will, so I'm grateful to you for highlighting these responses to his review. Thanks!

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