VoiceOfRa comments on Probabilities Small Enough To Ignore: An attack on Pascal's Mugging - Less Wrong

20 Post author: Kaj_Sotala 16 September 2015 10:45AM

You are viewing a comment permalink. View the original post to see all comments and the full post content.

Comments (176)

You are viewing a single comment's thread. Show more comments above.

Comment author: VoiceOfRa 05 October 2015 11:59:42PM 2 points [-]

Given your preferences, they do show what your utility function should be (up to affine transformation).

Assuming your preferences satisfy the axioms.

By completeness I assume you mean assigning a finite utility to every lottery, including the infinite ones.

No, by completeness I mean that for any two lotteries you prefer one over the other.

Why not reject completeness?

So why not reject it in the finite case as well?

The St. Petersburg lottery is plainly one that cannot exist.

Care to assign a probability to that statement.

Comment author: RichardKennaway 06 October 2015 01:00:30PM 0 points [-]

So why not reject it in the finite case as well?

Actually, I would, but that's digressing from the subject of infinite lotteries. As I have been pointing out, infinite lotteries are outside the scope of the VNM axioms and need additional axioms to be defined. It seems no more reasonable to me to require completeness of the preference ordering over St. Petersburg lotteries than to require that all sequences of real numbers converge.

Care to assign a probability to that statement.

"True." At some point, probability always becomes subordinate to logic, which knows only 0 and 1. If you can come up with a system in which it's probabilities all the way down, write it up for a mathematics journal.

If you're going to cite this (which makes a valid point, but people usually repeat the password in place of understanding the idea), tell me what probability you assign to A conditional on A, to 1+1=2, and to an omnipotent God being able to make a weight so heavy he can't lift it.

Comment author: VoiceOfRa 07 October 2015 03:54:00AM 1 point [-]

"True." At some point, probability always becomes subordinate to logic, which knows only 0 and 1. If you can come up with a system in which it's probabilities all the way down, write it up for a mathematics journal.

Ok, so care to present an a priori pure logic argument for why St. Petersburg lottery-like situations can't exist.

Comment author: RichardKennaway 07 October 2015 04:15:21PM -1 points [-]

Ok, so care to present an a priori pure logic argument for why St. Petersburg lottery-like situations can't exist.

FInite approximations to the St. Petersburg lottery have unbounded values. The sequence does not converge to a limit.

In contrast, a sequence of individual gambles with expectations 1, 1/2, 1/4, etc. does have a limit, and it is reasonable to allow the idealised infinite sequence of them a place in the set of lotteries.

You might as well ask why the sum of an infinite number of ones doesn't exist. There are ways of extending the real numbers with various sorts of infinite numbers, but they are extensions. The real numbers do not include them. The difficulty of devising an extension that allows for the convergence of all infinite sums is not an argument that the real numbers should be bounded.

Comment author: VoiceOfRa 08 October 2015 02:56:42AM *  1 point [-]

FInite approximations to the St. Petersburg lottery have unbounded values. The sequence does not converge to a limit.

They have unbounded expected values, that doesn't mean the St. Petersburg lottery can't exist, only that its expected value doesn't.