Meta Decision Theory and Newcomb's Problem

Don't worry, that's not an uncomfortable question. UDT and MDT are quite different. UDT is a first-order decision theory. MDT is a way of extending decision theories - so that you take into account uncertainty about which decision theory to use. (So, one can have meta causal decision theory, meta evidential decision theory, and (probably, thought I haven't worked through it) meta updateless decision theory.)

UDT, as I understand it (and note I'm not at all fluent in UDT or TDT) always one-boxes; whereas if you take decision-theoretic uncertainty into account you should sometimes one-box and sometimes two-box, depending on the relative value of the contents of the two boxes. Also, UDT gets what most decision-theorists consider the wrong answer in the smoking lesion case, whereas the account I defend, meta causal decision theory, doesn't (or, at least, doesn't, depending on one's credences in first-order decision theories).

To illustrate, consider the case:

High-Stakes Predictor II (HSP-II) Box C is opaque; Box D, transparent. If the Predictor predicts that you choose Box C only, then he puts one wish into Box C, and also a stick of gum. With that wish, you save the lives of 1 million terminally ill children. If he predicts that you choose both Box C and Box D, then he puts nothing into Box C. Box D — transparent to you — contains an identical wish, also with the power to save the lives of 1 million children, so if one had both wishes one would save 2 million children in total. However, Box D contains no gum. One has two options only: choose Box C only, or both Box C and Box D.

In this case, intuitively, should you one box, or two box? My view is clear: that if someone one-boxes in the above case, they made the wrong decision. And it seems to me that this is best explained with appeal to decision-theoretic uncertainty.

Other questions: Bostrom's parliamentary model is different. Between EDT and CDT, the intertheoretic comparisons of value are easy, so there's no need to use the parliamentary analogy - one can just straightforwardly take an expectation over decision theories.

Pascal's Mugging (aka the "Fanaticism" worry). This is a general issue for attempts to take normative uncertainty into account in one's decision-making, and not something I discuss in my paper. But if you're concerned about Pascal's mugging and, say, think that a bounded Decision Theory is the best way to respond to the problem - then at the meta level you should also have a bounded decision theory (and at the meta meta level, and so on).

From memory, Nozick explicitly disclaims the idea that his view might be a response to normative uncertainty. Rather, he claims that EDT and CDT both have normative force and so should both be taken into account. While this may appear to be window dressing, this will have fairly substantial impacts. In particular, no regress threatens Nozick but the regress issue is going to need to be responded to in the normative uncertainty case.

Thanks for mentioning this - I discuss Nozick's view in my paper, so I'm going to edit my comment to mention this. A few differences:

As crazy88 says, Nozick doesn't think that the issue is a normative uncertainty issue - his proposal is another first-order decision theory, like CDT and EDT. I argue against that account in my paper. Second, and more importantly, Nozick just says "hey, our intuitions in Newcomb-cases are stakes-sensitive" and moves on. He doesn't argue, as I do, that we can explain the problematic cases in the literature by appeal to decision-theoretic uncertainty. Nor does he use decision-theoretic uncertainty to respond to arguments in favour of EDT. Nor does he respond to regress worries, and so on.

I'm guessing yes. I'm also guessing this paper is a spin off from the question of Moral Uncertainty. Arguments about Moral uncertainty experience similar kinds of fragility (vicious regress) that need addressing.