Relevance of Subgame perfection. Seldin suggested subgame perfection as a refinement of Nash equilibrium which requires that decisions that seemed rational at the planning stage ought to still seem rational at the action stage. This at least suggests that we might want to consider requiring "subgame perfection" even if we only have a single player making two successive decisions.
Relevance of Footnote #4. This points out that one way to think of problems where a single player makes a series of decisions is to pretend that the problem has a series of players making the decisions - one decision per player, but that these fictitious players are linked in that they all share the same payoffs (but not necessarily the same information). This is a standard "trick" in game theory, but the footnote points out that in this case, since both fictitious players have the same information (because of the absent-mindedness) the game between driver-version-1 and driver-version-2 is symmetric, and that is equivalent to the constraint p1 = p2.
Does Footnote #4 really amount to "they had already argued for [just recalculating the planning-optimal solution]"? Well, no it doesn't really. I blew it in offering that as evidence. (Still think it is cool, though!)
Do they "argue for it" anywhere else? Yes, they do. Section 5, where they apply their methods to a slightly more complicated example, is an extended argument for the superiority of the planning-optimal solution to the action-optimal solutions. As they explain, there can be multiple action-optimal solutions, even if there is only one (correct) planning-optimal solution, and some of those action-optimal solutions are wrong *even though they appear to promise a higher expected payoff than does the planning optimal solution.
I can't see where they made this point. At the top of Section 4, they say "How, then, should the driver reason at the action stage?" and go on directly to describe action-optimality. If they said something like "One possibility is to just recompute and apply the planning-optimal solution. But if you insist ..." please point out where. See also page 108:
In our case, there is only one player, who acts at different times. Because of his absent-mindedness, he had better coordinate his actions; this coordination can take place only before he starts out at the planning stage. At that point, he should choose p1 . If indeed he chose p1 , there is no problem. If by mistake he chose p2 or p3 , then that is what he should do at the action stage. (If he chose something else, or nothing at all, then at the action stage he will have some hard thinking to do.)
If Aumann et al. endorse using planning-optimality at the action stage, why would they say the driver has some hard thinking to do? Again, why not just recompute and apply the planning-optimal solution?
I really don't see why you are having so much trouble parsing this. "If indeed he chose p1 , there is no problem" is an endorsement of the correctness of the planning-optimal solution. The sentence dealing with p2 and p3 asserts that, if you mistakenly used p2 for your first decision, then you best follow-up is to remain consistent and use p2 for your remaining two choices. The paragraph you quote to make your case is one I might well choose myself to make my case.
Edit: There are some asterisks in variable names in the original paper which I was unable to make work with the italics rules on this site. So "p2" above should be read as "p 2"
You can use a backslash to escape special characters in markdown.
If you type \*, that will show up as * in the posted text.
A common background assumption on LW seems to be that it's rational to act in accordance with the dispositions one would wish to have. (Rationalists must WIN, and all that.)
E.g., Eliezer:
And more recently, from AdamBell:
Within academic philosophy, this is the position advocated by David Gauthier. Derek Parfit has constructed some compelling counterarguments against Gauthier, so I thought I'd share them here to see what the rest of you think.
First, let's note that there definitely are possible cases where it would be "beneficial to be irrational". For example, suppose an evil demon ('Omega') will scan your brain, assess your rational capacities, and torture you iff you surpass some minimal baseline of rationality. In that case, it would very much be in your interests to fall below the baseline! Or suppose you're rewarded every time you honestly believe the conclusion of some fallacious reasoning. We can easily multiply cases here. What's important for now is just to acknowledge this phenomenon of 'beneficial irrationality' as a genuine possibility.
This possibility poses a problem for the Eliezer-Gauthier methodology. (Quoting Eliezer again:)
The problem, obviously, is that it's possible for irrational agents to receive externally-generated rewards for their dispositions, without this necessarily making their downstream actions any more 'reasonable'. (At this point, you should notice the conflation of 'disposition' and 'choice' in the first quote from Eliezer. Rachel does not envy Irene her choice at all. What she wishes is to have the one-boxer's dispositions, so that the predictor puts a million in the first box, and then to confound all expectations by unpredictably choosing both boxes and reaping the most riches possible.)
To illustrate, consider (a variation on) Parfit's story of the threat-fulfiller and threat-ignorer. Tom has a transparent disposition to fulfill his threats, no matter the cost to himself. So he straps on a bomb, walks up to his neighbour Joe, and threatens to blow them both up unless Joe shines his shoes. Seeing that Tom means business, Joe sensibly gets to work. Not wanting to repeat the experience, Joe later goes and pops a pill to acquire a transparent disposition to ignore threats, no matter the cost to himself. The next day, Tom sees that Joe is now a threat-ignorer, and so leaves him alone.
So far, so good. It seems this threat-ignoring disposition was a great one for Joe to acquire. Until one day... Tom slips up. Due to an unexpected mental glitch, he threatens Joe again. Joe follows his disposition and ignores the threat. BOOM.
Here Joe's final decision seems as disastrously foolish as Tom's slip up. It was good to have the disposition to ignore threats, but that doesn't necessarily make it good idea to act on it. We need to distinguish the desirability of a disposition to X from the rationality of choosing to do X.