Newcomb's Problem is effectively a problem about pre-commitment. Everyone agrees that if you have the opportunity to pre-commit in advance of Omega predicting you, then you ought to. The only question is what you ought to do if you either failed to do this or weren't given the opportunity to do this. LW-Style Decision Theories like TDT or UDT say that you should act as though you are pre-committed, while Casual Decision Theory says that it's too late.
Formal pre-commitments include things like rewriting your code, signing a legally binding contract, or providing assets as security. If set up correctly, they ensure that a rational agent actually keeps their end of the bargain. Of course, an irrational agent may still break their end of the bargain.
Effective pre-commitment describes any situation where an agent must (in the logical sense) necessarily perform an action in the future, even if there is no formal pre-commitment. If libertarian free will were to exist, then no one would ever be effectively pre-committed, but if the universe is deterministic, then we are effectively pre-committed to any choice that we make (quantum mechanics effectively pre-commits us to particular probability distributions, rather than individual choices, but for purposes of simplicity we will ignore this here and just assume straightforward determinism). This follows straight from the definition of determinism (more discussion about the philosophical consequences of determinism in a previous post).
One reason why this concept seems so weird is that there's absolutely no need for an agent that's effectively pre-committed to know that it is pre-committed until the exact moment when it locks in its decision. From the agent's perspective, it magically turns out to be pre-committed to whatever action it chooses, however, the truth is that the agent was always pre-committed to this action, just without knowing.
Much of the confusion about pre-commitment is about whether we should be looking at formal or effective pre-commitment. Perfect predictors only care about effective pre-commitment; for them formalities are unnecessary and possibly misleading. However, human-level agents tend to care much more about formal pre-commitments. Some people, like detectives or poker players, may be really good at reading people, but they're still nothing compared to a perfect predictor and most people aren't even this good. So in everyday life, we tend to care much more about formal pre-commitments when we want certainty.
However, Newcomb's Problem explicitly specifies a perfect predictor, so we shouldn't be thinking about human level predictors. In fact, I'd say that some of the emphasise on formal pre-commitment comes from anthropomorphizing perfect predictors. It's really hard for us to accept that anyone or anything could actually be that good and that there's no way to get ahead of it.
In closing, differentiating the two kinds of pre-commitment really clarifies these kinds of discussions. We may not be able to go back into the past and pre-commit to a certain cause of action, but we can take an action on the basis that it would be good if we had pre-committed to it and be assured that we will discover that we were actually pre-committed to it.
In particular, I'd argue that the paradoxical aspects of Newcomb's problem result from exactly this kind of confusion between the usual agent idealization and the fact that actual actors (human beings) are physical beings subject to the laws of physics. The apparent paradoxical aspects results because we are used to idealizing individual behavior in terms of agents where that formalism requires we specify the situation in terms of a tree of possibilities with each path corresponding to an outcome and with the payoff computed by looking at the path specified by all agent's choices (e.g. there is a node where the demon player chooses what money to put in the boxes and then there is a node where the human player, without knowledge of demon player's choices, decides to take both boxes or neither). The agent formalization (where 1 or 2 boxing is modeled as a subsequent choice) simply doesn't allow the content of the boxes to depend on whether or not the human agent chooses 1 or 2 boxes.
Of course, since actual people aren't ideal agents one can argue that something like the newcomb demon is physically possible but that's just a way of specifying that we are in a situation where the agent idealization breaks down.
This means there is simply no fact of the matter about how a rational agent (or whatever) should behave in newcomb type situations because the (usual) rational agent idealization is incompatible with the newcomb situation (ok, more technically you can model it that way but the choice of how to model it just unsatisfactorily builds in the answer by specifying how the payoff depends on 1 vs two boxing).
To sum up what the answer to the newcomb problem is depends heavily on how you preciscify the question. Are you asking whether humans who are disposed to decide in way A end up better of than humans disposed to behave in way B? In that case it's easy. But things like CDT, TDT etc.. don't claim to be producing facts of that kind but rather saying something about ideal rational agents of some kind which then just boringly depends on a ambiguities in what we mean by that.ideal rational agents.
Except if you actually go try and do the work people's pre-theoretic understanding of rationality doesn't correspond to a single precise concept.
Once you step into Newcomb type problems it's no longer clear how decision theory is supposed to correspond to the world. You might be tempted to say that decision theory tells you the best way to act...but it no longer does that since it's not that the two-boxer should have picked one box. The two-boxer was incapable of so picking and what EDT is telling you is something more like: you sho... (read more)