Eliezer_Yudkowsky comments on Ingredients of Timeless Decision Theory - Less Wrong

43 Post author: Eliezer_Yudkowsky 19 August 2009 01:10AM

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Comment author: Eliezer_Yudkowsky 22 August 2009 09:03:18PM 1 point [-]

By hypothesis, Omega on examining your code at 6:59, knows that you will self-modify at 7:00 and one-box thereafter.

CDT agents don't care. They aren't causing Omega to fill box B by changing their source code at 7pm, so they have no reason to change their source code in a way that takes only one box. The source code change only causes Omega to fill box B if Omega looks at their source code after 7pm. That is how CDT agents (unwisely) compute "causes".

Comment author: rwallace 23 August 2009 09:17:11AM 0 points [-]

Yes, but the CDT agent at seven o'clock is not being asked to choose one or two boxes. It has to choose between rewriting its algorithm to plain TDT (or DBDT or some variant that will one box), or to TDT with an exception clause "but use the old algorithm if you find out Omega's prediction was made before seven o'clock". Even by straight CDT, there is no motive for writing that exception.

Comment author: Eliezer_Yudkowsky 23 August 2009 07:34:58PM *  4 points [-]

Even by straight CDT, there is no motive for writing that exception.

This is the point at which I say "Wrong" and "Read the literature". I'm not sure how I can explain this any more clearly than I have already, barring a full-fledged sequence. At 7pm the CDT agent calculates that if it modifies its source to use the old algorithm in cases where Omega saw the code before 7pm, it will get an extra thousand dollars on Newcomb's Problem, since it will take box A which contains an additional thousand dollars, and since its decision to modify its code at 7pm has no effect on an Omega who saw the code before 7pm, hence no effect on whether box B is full. It does not reason "but Omega knows I will change my code". If it reasoned that way it would be TDT, not CDT, and would one-box to begin with.

Comment author: rwallace 23 August 2009 11:06:26PM 0 points [-]

Actually I will add another comment because I can now articulate where the ambiguity comes in: how you add self modification to CDT (which doesn't have it in the usual form); I've been assuming the original algorithm doesn't try to micromanage the new algorithm's decisions (which strikes me as the sensible way, not least because it gives better results here); you've been assuming it does (which I suppose you could argue, is more true to the spirit of the original CDT).

Comment author: rwallace 23 August 2009 10:21:28PM 0 points [-]

I still disagree, but I agree that we have hit the limits of discussion in this comment thread; fundamentally this needs to be analyzed in a more precise language than English. We can revisit it if either of us ever gets to actually programming anything like this.