RichardKennaway comments on St. Petersburg Mugging Implies You Have Bounded Utility - Less Wrong

10 Post author: TimFreeman 07 June 2011 03:06PM

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Comment author: RichardKennaway 15 June 2011 08:25:23PM 2 points [-]

Can you come up with a historical example of a mathematical or scientific problem being solved - not made to work for some specific purpose, but solved completely - with a principled hack?

Limited comprehension in ZF set theory is the example I had in mind in coining the term "principled hack". Russell said to Frege, "what about the set of sets not members of themselves?", whereupon Frege was embarrassed, and eventually a way was found of limiting self-reference enough to avoid the contradiction. There's a principle there -- unrestricted self-reference can't be done -- but all the methods of limiting self-reference that have yet been devised look like hacks. They work, though. ZF appears to be consistent, and all of mathematics can be expressed in it. As a universal language, it completely solves the problem of formalising mathematics.

(I am aware that there are mathematicians who would disagree with that triumphalist claim, but as far as I know none of them are mainstream.)

Comment author: [deleted] 19 June 2011 10:32:06PM 1 point [-]

Being a mathematician who at least considers himself mainstream, I would think that ZFC and the existence of a large cardinal is probably the minimum one would need to express a reasonable fragment of mathematics.

If you can't talk about the set of all subsets of the set of all subsets of the real numbers, I think analysis would become a bit... bondage and discipline.

Comment author: RichardKennaway 20 June 2011 08:13:24AM 0 points [-]

If you can't talk about the set of all subsets of the set of all subsets of the real numbers

Surely the power set axiom gets you that?

Comment author: [deleted] 20 June 2011 11:01:31AM 0 points [-]

That it exists, yes. But what good is that without choice?

Comment author: RichardKennaway 20 June 2011 11:28:32AM *  0 points [-]

Ok, ZFC is a more convenient background theory than ZF (although I'm not sure where it becomes awkward to do without choice). That's still short of needing large cardinal axioms.

Comment author: endoself 19 June 2011 09:44:08PM 0 points [-]

The idea of programming ZF into an AGI horrifies my aesthetics, but that is no reason not to use it (well it is an indication that it might not be a good idea but in this specific case ZF does have the evidence on its side). If expected utility, or anything else necessary for an AGI, could benefit from a principled hack as well-tested as limited comprehension, I would accept it.