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TheOtherDave comments on The Useful Idea of Truth - Less Wrong

77 Post author: Eliezer_Yudkowsky 02 October 2012 06:16PM

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Comment author: TheOtherDave 03 October 2012 02:10:21PM 2 points [-]

I don't think that "You should two-box in Newcomb's problem." is actually a normative statement, even if it contains a "should": you can rephrase it epistemically as "If you two-box in Newcomb's problem then you will maximize your expected utility".

Well, sure, a utilitarian can always "rephrase" should-statements that way; to a utilitarian what "X should Y" means is "Y maximizes X's expected utility." That doesn't make "X should Y" not a normative statement, it just means that utilitarian normative statements are also objective statements about reality.

Conversely, I'm not sure a deontologist would agree that you can rephrase one as the other... that is, a deontologist might coherently (and incorrectly) say "Yes, two-boxing maximizes expected utility, but you still shouldn't do it."

Comment author: V_V 03 October 2012 02:57:41PM *  0 points [-]

I think you are conflating two different types of "should" statements: moral injunctions and decision-theoretical injunctions.

The statement "You should two-box in Newcomb's problem" is normally interpreted as a decision-theoretical injunction. As such, it can be rephrased epistemically as "If you two-box in Newcomb's problem then you will maximize your expected utility".

But you could also interpret the statement "You should two-box in Newcomb's problem" as the moral injunction "It is morally right for you to two-box in Newcomb's problem". Moral injunctions can't be rephrased epistemically, at least unless you assume a priori that there exist some external moral truths that can't be further rephrased.

The utilitarianist of your comment is doing that. His actual rephrasing is "If you two-box in Newcomb's problem then you will maximize the expected universe cumulative utility". This assumes that:

  • This universe cumulative utility exists as an external entity

  • The statement "It is morally right for you to maximize the expected universe cumulative utility" exists as an external moral truth.