Comment author:roystgnr
13 March 2012 06:24:13AM
*
2 points
[-]

If you look at the assumptions behind VNM, I'm not at all sure that the "torture is worse than any amount of dust specks" crowd would agree that they're all uncontroversial.

In particular the axioms that Wikipedia labels (3) and (3') are almost begging the question.

Imagine a utility function that maps events, not onto R, but onto (R x R) with a lexicographical ordering. This satisfies completeness, transitivity, and independence; it just doesn't satisfy continuity or the Archimedian property.

But is that the end of the world? Look at continuity: if L is torture plus a dust speck (utility (-1,-1)). M is just torture (utility (-1,0)) and N is just a dust speck ((0,-1)), then must there really be a probability p such that pL + (1-p)N = M? Or would it instead be permissable to say that for p=1, torture plus dust speck is still strictly worse than torture, whereas for any p<1, any tiny probability of reducing the torture is worth a huge probabilty of adding that dust speck to it?

## Comments (300)

Old*2 points [-]If you look at the assumptions behind VNM, I'm not at all sure that the "torture is worse than any amount of dust specks" crowd would agree that they're all uncontroversial.

In particular the axioms that Wikipedia labels (3) and (3') are almost begging the question.

Imagine a utility function that maps events, not onto R, but onto (R x R) with a lexicographical ordering. This satisfies completeness, transitivity, and independence; it just doesn't satisfy continuity or the Archimedian property.

But is that the end of the world? Look at continuity: if L is torture plus a dust speck (utility (-1,-1)). M is just torture (utility (-1,0)) and N is just a dust speck ((0,-1)), then must there really be a probability p such that pL + (1-p)N = M? Or would it instead be permissable to say that for p=1, torture plus dust speck is still strictly worse than torture, whereas for any p<1, any tiny probability of reducing the torture is worth a huge probabilty of adding that dust speck to it?

(edited to fix typos)