lackofcheese comments on Causal decision theory is unsatisfactory - LessWrong

20 Post author: So8res 13 September 2014 05:05PM

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Comment author: shminux 13 September 2014 07:28:14PM 10 points [-]

I suspect that CDT seems not suitable for Newcomb-like problems because it tends to be applied to non-existent outcomes. If the outcome is not in the domain, you should not be calculating its utility. In the PD example CD and DC are not valid outcomes for clones. Similarly, two-boxing and getting $1001k is not a valid outcome in Newcomb. If you prune the decision tree of imaginable but non-existing branches before applying a decision theory, many differences between CDT and EDT tend to go away.

Comment author: lackofcheese 14 September 2014 02:13:10AM 9 points [-]

Moreover, if you prune the decision tree of all branches bar one then all decision algorithms will give the same (correct) answer!

It's totally OK to add a notion of pruning in, but you can't really say that your decision algorithm of "CDT with pruning" makes sense unless you can specify which branches ought to be pruned, and which ones should not. Also, outright pruning will often not work; you may only be able to rule out a branch as highly improbable rather than altogether impossible.

In other words, "pruning" as you put it is simply the same thing as "recognizing logical connections" in the sense that So8res used in the above post.

Comment author: private_messaging 14 September 2014 12:45:52PM 3 points [-]

Well, a decision theory presumably is applied to some model of the physics, so that your agent can for example conclude that jumping out of a 100th floor window would result in it hitting ground at a high velocity. Finding that a hypothetical outcome is physically impossible would fall within the purview of the model of physics.