I suggest, as a useful mantra, Jeffrey’s (1983, 16) slogan “Choose for the person you expect to become once you have chosen.”
Whoa, no. That’s a bad mantra. Wireheading, quantum immortality, doing meth—these are bad things.
The idea in the paper is is that you should decide by letting your “future selves” “vote,” justified by the mantra above. And so their entire result is that in cases where your “future selves” who use different decision theories have different preference orderings, Arrow’s theorem applies.
This not only requires you to throw away the cardinal information as gwern says, it only works if you make your decisions according to the mantra above! A reductio ad absurdum of this position would be that it can’t even distinguish CDT from evil-CDT, which is where you always choose the locally worst option. Their result is really just the statement “some decision theories have different preference orderings,” and should not be taken as a test of whether or not some decision theories are better than others.
Whoa, no. That’s a bad mantra. Wireheading, quantum immortality, doing meth—these are bad things.
Briggs is here primarily considering cases where your preferences don’t change as a result of your decision (but where your credences might). If we’re interested in criticising the argument precisely as stated then perhaps this is a reasonable criticism but it’s not an interesting criticism of Briggs’ view which is to do with how we reason in cases where our decision gives us new information about the state of the world (ie. about changing credences not changing utilities).
This not only requires you to throw away the cardinal information as gwern says
Again, it is not clear that this is an interesting criticism. The result doesn’t rely on cardinal values but it does apply to agents with cardinal values. This makes it a stronger more powerful result (rather than an uninteresting result which doesn’t apply to actual theories). The result only relies on the ordinal rankings of outcomes but it causes problems for theories that utilise cardinal values (like decision theory). So Gwern notes that “a lot of voting paradoxes are resolved with additional information. (For example, Arrow’s paradox is resolved with cardinal information.)”. This isn’t true with Briggs’ argument—it can’t simply be resolved by having cardinal preferences.
A reductio ad absurdum of this position would be that it can’t even distinguish CDT from evil-CDT, which is where you always choose the locally worst option. Their result is really just the statement “some decision theories have different preference orderings,”
Again, not clear that this is an interesting criticism. Briggs’ isn’t trying to develop a necessary and sufficient criteria for theory adequacy so it’s no surprise that her paper doesn’t determine which of CDT and evil-CDT one should follow. She’s just introducing two necessary criteria for theory adequacy and presenting a proof that no theory can meet these. So both CDT and evil-CDT fail to be entirely adequate theories—that’s all she is trying to establish. Of course, we also want a tool that can tell us that CDT is a more adequate theory than evil-CDT but that’s not the tool that Briggs is discussing here so it seems unreasonable to criticise her on the grounds that she fails to achieve some aim that’s tangential to her purpose.
This isn’t true with Briggs’ argument—it can’t simply be resolved by having cardinal preferences.
Yup, I missed that a year ago.
evil-CDT
I’m not sure where I was going with that either.
Briggs is here primarily considering cases where your preferences don’t change as a result of your decision (but where your credences might).
True. Though on the other hand, the smoking lesion problem (and variants) is pretty much the credence-changing equivalent of doing meth :P I still think the requirements are akin to “let’s find a decision theory that does meth but never has anything bad happen to it.”
In the paper:
Whoa, no. That’s a bad mantra. Wireheading, quantum immortality, doing meth—these are bad things.
The idea in the paper is is that you should decide by letting your “future selves” “vote,” justified by the mantra above. And so their entire result is that in cases where your “future selves” who use different decision theories have different preference orderings, Arrow’s theorem applies.
This not only requires you to throw away the cardinal information as gwern says, it only works if you make your decisions according to the mantra above! A reductio ad absurdum of this position would be that it can’t even distinguish CDT from evil-CDT, which is where you always choose the locally worst option. Their result is really just the statement “some decision theories have different preference orderings,” and should not be taken as a test of whether or not some decision theories are better than others.
Briggs is here primarily considering cases where your preferences don’t change as a result of your decision (but where your credences might). If we’re interested in criticising the argument precisely as stated then perhaps this is a reasonable criticism but it’s not an interesting criticism of Briggs’ view which is to do with how we reason in cases where our decision gives us new information about the state of the world (ie. about changing credences not changing utilities).
Again, it is not clear that this is an interesting criticism. The result doesn’t rely on cardinal values but it does apply to agents with cardinal values. This makes it a stronger more powerful result (rather than an uninteresting result which doesn’t apply to actual theories). The result only relies on the ordinal rankings of outcomes but it causes problems for theories that utilise cardinal values (like decision theory). So Gwern notes that “a lot of voting paradoxes are resolved with additional information. (For example, Arrow’s paradox is resolved with cardinal information.)”. This isn’t true with Briggs’ argument—it can’t simply be resolved by having cardinal preferences.
Again, not clear that this is an interesting criticism. Briggs’ isn’t trying to develop a necessary and sufficient criteria for theory adequacy so it’s no surprise that her paper doesn’t determine which of CDT and evil-CDT one should follow. She’s just introducing two necessary criteria for theory adequacy and presenting a proof that no theory can meet these. So both CDT and evil-CDT fail to be entirely adequate theories—that’s all she is trying to establish. Of course, we also want a tool that can tell us that CDT is a more adequate theory than evil-CDT but that’s not the tool that Briggs is discussing here so it seems unreasonable to criticise her on the grounds that she fails to achieve some aim that’s tangential to her purpose.
Yup, I missed that a year ago.
I’m not sure where I was going with that either.
True. Though on the other hand, the smoking lesion problem (and variants) is pretty much the credence-changing equivalent of doing meth :P I still think the requirements are akin to “let’s find a decision theory that does meth but never has anything bad happen to it.”