Gary_Drescher comments on A problem with Timeless Decision Theory (TDT) - Less Wrong

36 Post author: Gary_Drescher 04 February 2010 06:47PM

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Comment author: Gary_Drescher 05 February 2010 02:12:29AM *  3 points [-]

I think this problem is based (at least in part) on an incoherence in the basic transparent box variant of Newcomb's problem.

If the subject of the problem will two-box if he sees the big box has the million dollars, but will one-box if he sees the big box is empty. Then there is no action Omega could take to satisfy the conditions of the problem.

The rules of the transparent-boxes problem (as specified in Good and Real) are: the predictor conducts a simulation that tentatively presumes there will be $1M in the large box, and then puts $1M in the box (for real) iff the simulation showed one-boxing. So the subject you describe gets an empty box and one-boxes, but that doesn't violate the conditions of the problem, which do not require the empty box to be predictive of the subject's choice.

Comment author: JGWeissman 05 February 2010 03:25:52AM 0 points [-]

I drew a causal graph of this scenario (with the clarification you just provided), and in order to see the problem with TDT you describe, I would have to follow a causation arrow backwards, like in Evidential Decision Theory, which I don't think is how TDT handles counterfactuals.

Comment author: Gary_Drescher 05 February 2010 03:11:51PM 1 point [-]

The backward link isn't causal. It's a logical/Platonic-dependency link, which is indeed how TDT handles counterfactuals (i.e., how it handles the propagation of "surgical alterations" to the decision node C).

Comment author: JGWeissman 05 February 2010 06:19:49PM 0 points [-]

My understanding of the link in question, is that the logical value of the digit of pi causes Omega to take the physical action of putting the money in the box.

See Eliezer's second approach:

2) Treat differently mathematical knowledge that we learn by genuinely mathematical reasoning and by physical observation. In this case we know (D xor E) not by mathematical reasoning, but by physically observing a box whose state we believe to be correlated with D xor E. This may justify constructing a causal DAG with a node descending from D and E, so a counterfactual setting of D won't affect the setting of E.

Comment author: JGWeissman 05 February 2010 02:59:18AM 0 points [-]

Ah, I was working from different assumptions. That at least takes care of the basic clear box variant. I will have to think about the digit of pi variation again with this specification.

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