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Tyrrell_McAllister comments on Second order logic, in first order set-theory: what gives? - Less Wrong Discussion

10 Post author: Stuart_Armstrong 23 February 2012 12:29PM

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Comment author: Tyrrell_McAllister 23 February 2012 05:16:02PM *  8 points [-]

The standard model of the reals, the unique field that obeys the second order axioms inside standard models of set theory...

(Emphasis added.)

Are there such things as "standard models of set theory"? This page from a book on model theory says that there is no standard model. The closest things, it says, are something called "natural models". I only glanced at it, but the notion of "natural model" appears to be a second-order concept that depends on the set theory with which you started.

Comment author: Stuart_Armstrong 24 February 2012 09:40:39AM 0 points [-]

Yes, I'm not sure about this myself. But people do seem to feel that some models of set theory are non-standard (eg countable models), and that there is a standard model of the reals. I get the impression that some models of set theory are "standardler" than others...