JeremyHahn comments on Second-Order Logic: The Controversy - Less Wrong

24 Post author: Eliezer_Yudkowsky 04 January 2013 07:51PM

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Comment author: JeremyHahn 07 January 2013 06:50:35PM 3 points [-]

I do not think the situation is as simple as you claim it to be. Consider that a category is more general than a monoid, but there are many interesting theorems about categories.

As far as foundations for mathematical logic go, any one interested in such things should be made aware of the recent invention of univalent type theory. This can be seen as a logic which is inherently higher-order, but it also has many other desirable properties. See for instance this recent blog post: http://golem.ph.utexas.edu/category/2013/01/from_set_theory_to_type_theory.html#more

That univalent type theory is only a few years old is a sign we are not close to fully understanding what foundational logic is most convenient. For example, one might hope for a fully directed homotopy type theory, which I don't doubt will appear a few years down the line.

Comment author: Qiaochu_Yuan 07 January 2013 10:52:00PM 0 points [-]

Sure. It has of course been the case that careful increases in generality have also led to increases in power (hence the weasel word "usually"). There is something like a "production-possibilities frontier" relating generality and power, and some concepts are near the frontier (and so one can't generalize them without losing some power) while some are not.