Comment by WJ on Newcomb's Problem and Regret of Rationality · 2009-03-05T08:58:00.000Z · LW · GW

I think I've solved it.

I'm a little late to this, and given the amount of time people smarter than myself have spent thinking about this it seems naive even to myself to think that I have found a solution to this problem. That being said, try as I might, I can't find a good counter argument to this line of reasoning. Here goes...

The human brain's function is still mostly a black box to us, but the demonstrated predictive power of this alien is strong evidence that this is not the case with him. If he really can predict human decisions, than the mere fact that you are choosing one box is the best way for you to ensure that will be what is predicted.

The standard attack on this line of reasoning seems to be that since his prediction happened in the past, your decision can't influence it. But it already has influenced it. He was aware of the decision before you made it (evidenced by his predictive power). In fact, it is not really a decision in the sense of "freely" choosing one of two options (in the way that most people use "freely" at least). Think of this decision as just extremely complicated and seemingly unpredictable data analysis, where the unpredictability comes from never being able to know intimately every part of the decision process and the inputs. But if one could perfectly crack the "black box" of your decision, as this alien appears to have done (at least this seems by far the most plausible explanation to me) then one could predict decisions with the accuracy the alien possesses. In other words, the gears were already in motion for your decision to be made, and the alien was already witness whether you realized it or not. In that sense you aren't making your decision afterwords when you think you are, you are actually realizing the decision that you were already set up to make at an earlier time.

If you agree with what I have written above, your obvious best decision is to just go ahead and pick one box, and hope that the alien would have predicted this. Based on the evidence, that will probably be enough to make the one million show up. Deciding instead to go for two boxes for any reason whatsoever will probably mean that the million won't be there. The time issue is just an illusion caused by your imperfect knowledge and data processing that takes time.