Peter Klein Doesn't Grasp the History of Science

Klein is trying to knock Krugman by rejecting the idea that we can have a science of higher-level phenomena before understanding the lower levels that make the higher level up:

"Methodological individualists don’t deny that there are interesting macro-level regularities that should be recorded and studied, only that claims about them don’t reach the status of science until we understand the underlying causal mechanisms."

And that denial is nonsense. Kepler certainly was doing science, and good science, when he developed his laws of planetary motion, without having any idea what underlay those laws. And so was Newton, when he developed his law of universal gravitation, without the least notion of what underlying casual mechanisms were behind this regularity -- something he freely admitted himself. And both physics and chemistry would have been stopped in their tracks by trying to be Kleinian "sciences": they progressed for centuries before it was even clear that atoms existed.

Peter has to go so far as to claim that Darwin's theory of evolution, generally acknowledged as one of the greatest scientific accomplishments ever, was not a scientific theory at all!

Well, when you try to spit into the headwind of the obvious (which is that you can have perfectly sound, completely scientific macro theories way, way before you know any microfoundations whatsoever), it will tend to come back at you!

To Klein's credit, when someone in the comments noted similar things to what I point out here, Peter backed off. But not far enough to admit the truth, which is that Krugman was right in the first place, and did not deserve Peter's "ugh" or accusation of "scientism."


  1. I imagine Klein will retract his post to applying primarily to Social Science.

    Of course one wonders why he didn't bother to make that clear in his blog post.

    1. That is what he has done. But earlier he specifically claimed just the opposite.

      And, I think it is just as false for social science as it is for physical science.

  2. I really think Gene's right here although I see a clear case for methodological dualism. I just think that this is only a matter of the impossibility of performing controlled experiments anywhere near the degree as it is possible in natural sciences.

    Yet in regard to the relationship between micro and macro I do think they are perfectly analog. In both cases I’d argue that only having macro theories without understanding the micro world brings a certain amount of uncertainty into the viability of the macro theory. You never know if there are variables that under certain circumstances change and maybe wreck your whole macro theory. Those variables might just be triggered through the very intervention that was designed according to a (maybe wrong or incomplete) macro theory.

  3. Great post. I take a strange pleasure in seeing the usual suspects trot out their references to the physical sciences, not necessarily grasping what that might entail.

    On evolution, I would note that Darwin and Wallace managed to establish a pretty solid account of things despite their ignorance of genetics. (Google "pangenesis" kids!)

    Actually, on the subject of genetics, Mendel managed pretty handily even though he knew nothing about DNA...


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