MrMind comments on Decision Theories: A Less Wrong Primer - Less Wrong

69 Post author: orthonormal 13 March 2012 11:31PM

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Comment author: scmbradley 17 March 2012 12:41:11PM 0 points [-]

See mine and orthonormal's comments on the PD on this post for my view of that.

The point I'm struggling to express is that I don't think we should worry about the thought experiment, because I have the feeling that Omega is somehow impossible. The suggestion is that Newcomb's problem makes a problem with CDT clearer. But I argue that Newcomb's problem makes the problem. The flaw is not with the decision theory, but with the concept of such a predictor. So you can't use CDT's "failure" in this circumstance as evidence that CDT is wrong.

Here's a related point: Omega will never put the money in the box. Smith act like a one-boxer. Omega predicts that Smith will one-box. So the million is put in the opaque box. Now Omega reasons as follows: "Wait though. Even if Smith is a one-boxer, now that I've fixed what will be in the boxes, Smith is better off two-boxing. Smith is smart enough to realise that two-boxing is dominant, once I can't causally affect the contents of the boxes." So Omega doesn't put the money in the box.

Would one-boxing ever be advantageous if Omega were reasoning like that? No. The point is Omega will always reason that two-boxing dominates once the contents are fixed. There seems to be something unstable about Omega's reasoning. I think this is related to why I feel Omega is impossible. (Though I'm not sure how the points interact exactly.)

Comment author: MrMind 11 April 2012 09:49:50AM 0 points [-]

"Wait though. Even if Smith is a one-boxer, now that I've fixed what will be in the boxes, Smith is better off two-boxing. Smith is smart enough to realise that two-boxing is dominant, once I can't causally affect the contents of the boxes." So Omega doesn't put the money in the box.

That line of reasoning is though available to Smith as well, so he can choose to one-boxing because he knows that Omega is a perfect predictor. You're right to say that the interplay between Omega-prediction-of-Smith and Smith-prediction-of-Omega are in a meta-stable state, BUT: Smith has to decide, he is going to make a decision, and so whatever algorithm it implements, if it ever goes down this line of meta-stable reasoning, must have a way to get out and choose something, even if it's just bounded computational power (or the limit step of computation in Hamkins infinite Turing machine). But since Omega is a perfect predictor, it will know that and choose accordingly. I have the feeling that Omega existence is something like an axiom, you can refuse or accept it and both stances are coherent.