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Hi Eric,

Thanks for this. These are all very good points, so I have little to say in reply.

I think there's something very confused in the way neoclassical economists handle the idea of observer-independence (or perhaps background-independence). This comes across especially in Robert Lucas' stuff. I'm going to put some thoughts on that in a post I'm writing partially in response to your post on Rosenberg on Krugman. It seemed like a neat historical angle to try to hang the blame for this on Friedman, but probably that's unfair!

Benj Hellie

"The second great modern crisis in the foundations of mathematics—precipitated in 1931 by Gödel's proof that there are bound to be undecidable statements in arithmetic—has its
companion-piece in physics in Heisenberg's indeterminacy principle." — WV Quine, 'On what there is', /Review of Metaphysics/, 1948, 38.

Alexander Douglas

Fascinating - thanks!

Perhaps this is the origin of Friedman's idea, or perhaps it shares with it a common origin (Carnap?).

But the analogy Quine draws doesn't have to do with observer-dependence as such. Rather, the point seems to concern ontology rather than methodology. In particular, Quine's claim seems to be that the posits of physics are revealed by Heisenberg's indeterminacy principle to be part of a 'mythology', as the posits of set theory are revealed to be part of a 'mythology' by Gödel. A bold claim! But a different one, I think, from that made by Friedman.

Indeed, I'm coming around to the view that what Friedman says is not implausible; I'm not sure I could say the same for Quine's assertion. (See my discussion with Richard Zach: http://originofspecious.wordpress.com/2014/09/23/an-exchange-with-richard-zach-about-my-friedmangodel-post/)

Alan Nelson

I'm no fan of MF's famous article. But Eric's quote from MPE strikes me as appropriately guarded. He writes 'counterpart', not 'exact analogy.' And couldn't the "general principle" he wonders about be something as bland as "Odd things happen to theories when some kind of self-referentiality is introduced"?

Alan Nelson

Now I've seen Benj Hellie's nice reminder. Quine's use of 'companion-piece' is even more measured than Friedman's "counterpart."

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Here's a link to my past blogging (and discussions involving me) at: New APPS.


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