Academian comments on Newcomb's problem happened to me - Less Wrong

37 Post author: Academian 26 March 2010 06:31PM

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Tags: newcomblike kavka causal timeless decision theory

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Comment author: taw 26 March 2010 07:09:12PM -1 points [-]

If precommitment is observable and unchangeable, then order of action is:

  • Joe: precommit or not
  • Kate: accept or not - knowing if Joe precommitted or not
  • Joe: breakup (assuming no precommitment)

If precommitment is not observable and/or changeable, then it can be rearranged, and we have:

  • Kate: accept or not - not having any clue what Joe did
  • Joe: breakup or not

Or in the most complex situation, with 3 probabilistic nodes:

  • Joe: precommit or not
  • Nature: Kate figures out what Joe did correctly or not
  • Kate: accept or not
  • Nature: Marriage happy or unhappy
  • Nature: Joe changes mind or not
  • Joe: breakup or not

None of these is remotely Newcombish. You only get Newcomb paradox when you assume causal loop, and try to solve the problem using tools devised for situations without causal loops.

Comment author: Academian 26 March 2010 07:30:44PM *  1 point [-]

My pre-sponse to this is in footnote 2:

If you care about "causal reasoning", the other half of what's supposed to make Newcomb confusing, then Joe's problem is more like Kavka's (so this post accidentally shows how Kavka and Newcomb are similar). But the distinction is instrumentally irrelevant: the point is that he can benefit from decision mechanisms that are evidential and time-invariant, and you don't need "unreasonable certainties" or "paradoxes of causality" for this to come up.

Comment author: taw 26 March 2010 07:47:06PM 0 points [-]

There is no need for time-invariance. The most generic model (2 Joe nodes; 1 Kate note; 3 Nature nodes) of vanilla decision theory perfectly explains the situation you're talking about - unless you postulate some causal loops.

Comment author: Academian 26 March 2010 07:51:43PM *  0 points [-]

Joe's problem is more like Kavka's (so this post accidentally shows how Kavka and Newcomb are similar)

Is that not the simplicity you're interested in?

Comment author: taw 26 March 2010 08:04:06PM -1 points [-]

And in Kavka's problem there's no paradox unless we assume causal loops (billionaire knows now if you're going to decide to drink the toxin or not tomorrow), or leave the problem ambiguous (so can you change or mind or not?).

Comment author: Academian 26 March 2010 08:12:56PM 3 points [-]

You'll notice I didn't once use the word "paradox" ;)

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