I think I’ve figured out the answer to my question.
The related scenario: You’re stuck in the desert without water (or money) and a car offers to give you a lift if, when you reach the town, you pay them money. But you’re both perfectly rational so you know when you reach town, you would gain nothing by giving the person the money then. You say, “Yes” but they know you’re lying and so drive off.
If you use a decision theory which would have you give them the money once you reach town, you end up better off (ie. safely in town), even though the decision to give the money may seem stupid once you’re in town.
From the perspective of t = 2 (ie. after the event), giving up the money looks stupid, you’re in town. But if you didn’t follow that decision theory, you wouldn’t be in town, so it is beneficial to follow that decision theory.
Similarly, at t = 2 in the counterfactual mugging, giving up the money looks stupid. But if you didn’t follow that decision theory, you would never have had the opportunity to win a lot more money. So once again, following a decision theory which involves you acting as if you precommitted is beneficial.
So by that analysis: My mistake was asking what the beneficial action was at t = 2. Whereas, the actual question is, what’s the beneficial decision theory to follow.
Sounds right to me. I had actually written a blog post recently that explores the desert problem (aka Parfit’s Hitchhiker) that you might be interested in. I think it also sheds some light on why humans (usually) obey a decision theory that would win on Parfit’s Hitchhiker.
I think I’ve figured out the answer to my question.
The related scenario: You’re stuck in the desert without water (or money) and a car offers to give you a lift if, when you reach the town, you pay them money. But you’re both perfectly rational so you know when you reach town, you would gain nothing by giving the person the money then. You say, “Yes” but they know you’re lying and so drive off.
If you use a decision theory which would have you give them the money once you reach town, you end up better off (ie. safely in town), even though the decision to give the money may seem stupid once you’re in town.
From the perspective of t = 2 (ie. after the event), giving up the money looks stupid, you’re in town. But if you didn’t follow that decision theory, you wouldn’t be in town, so it is beneficial to follow that decision theory.
Similarly, at t = 2 in the counterfactual mugging, giving up the money looks stupid. But if you didn’t follow that decision theory, you would never have had the opportunity to win a lot more money. So once again, following a decision theory which involves you acting as if you precommitted is beneficial.
So by that analysis: My mistake was asking what the beneficial action was at t = 2. Whereas, the actual question is, what’s the beneficial decision theory to follow.
Does my understanding seem correct?
Sounds right to me. I had actually written a blog post recently that explores the desert problem (aka Parfit’s Hitchhiker) that you might be interested in. I think it also sheds some light on why humans (usually) obey a decision theory that would win on Parfit’s Hitchhiker.