So you need some explanation of why it is that nearly all the decision-theory experts—who write monstrously complicated papers with math that would go over your head—think FDT is wrong, but intro philosophy students who know almost nothing about decision theory think that it’s right. In general, you should be skeptical of views that are rejected by ~100% of relevant experts, even after considering them at length.
This is an incorrect characterization of the field. If you define a “relevant expert” as an academic who publishes exclusively in academic philosophy journals (which are mostly read, at best, by other academics), then 15 years ago that might have been a valid (if lame) argument from authority / status. But these days, the most accomplished and high impact philosophers do at least some of their work in industry (e.g. frontier AI labs and non-university-backed research orgs), and a significant chunk of them accept some flavor of FDT as true.
“Adopt FDT” is probably too strong as a rephrasing; by “accept some flavor of FDT as true”, I intended to include anyone who one-boxes and / or cooperates in the prisoner’s dilemma because they disagree with you and academic-only philosophers on this:
One is called causal decision theory (CDT). I’m trying to be impartial, so I won’t tell you that it’s (probably) the correct view.
Robert Wiblin: So you think it’s the case that when it comes to programming an AI, there’s actually a lot of agreement on what kind of decision theory it should be using in practice. Or at least, people agree that it needn’t be causal decision theory, even though philosophers think in some more fundamental sense causal decision theory is the right decision theory.
Paul Christiano: I think that’s right. I don’t know exactly what… I think philosophers don’t think that much about that question. But I think it’s not a tenable position, and if you really got into an argument with philosophers it wouldn’t be a tenable position that you should program your AI to use causal decision theory.
Of course there’s still a bunch of intra-rationalist and AI researcher disagreement on the specifics of FDT / UDT, e.g. a bunch of them probably disagree specifically because of updatelessness / EDT-with-tickle reasons, which are (debatably) not just “some flavor of FDT” as I said above.
IDK who exactly the most prominent people who have published specific thoughts on this are, but as a starting point the MacAskill post from 2019 that you cited got a bunch of substantive replies. I didn’t check all of their credentials / accomplishments and what they’re up to these days, but I suspect the real locus of our disagreement is more about the bounds of who qualifies as a philosopher / expert. I think “academic philosophy credentials” are not a good proxy for legible philosophy expertise (see sibling reply for more).
A big chunk of philosophers one-box. These people generally adopt evidential decision theory. They also cooperate in PD with twin. So no, FDT isn’t just the same as one boxing. If it was, then all EDTers would be FDTers.
I don’t think you should program an AI to follow CDT. This is because decision theories are theories of which actions are rational, not the dispositions that you want to have. So I agree with Christiano—this obviously can’t be the criterion for being a functional decision theorist.
Here’s one test: there is not a single person, to the best of my knowledge, anywhere in the world who adopts FDT and has a Ph.D in philosophy. This fact is surprising if it’s the right view.
Here’s one test: there is not a single person, to the best of my knowledge, anywhere in the world who adopts FDT and has a Ph.D in philosophy. This fact is surprising if it’s the right view.
False:
With that said I was a CDTer who became an FDTer and also a rationalist who became an empiricist so maybe it’s my job to bring balance to the force. (source)
Tyler holds a PhD in analytic philosophy and democratic theory from Rutgers University (source)
Insofar as we think we should defer to some extent to [group of people] on [topic], shouldn’t we defer to [group of people whose job it is to scrutinize arguments on that topic] more so than [group of people who “are most accomplished and high impact”]? What does the latter have to do with their expertise about decision theory?
As a starting point / outside view heuristic, maybe? But I think this:
> [group of people whose job it is to scrutinize arguments on that topic]
Is not a particularly good description of what academia and the academic peer review process is actually doing in many fields, including academic philosophy. Philosophy is not the worst field in terms of pathologies of academia, but IMO it is punching far below its weight given the intellectual horsepower and human capital it attracts. Compare to academic economics: https://marginalrevolution.com/marginalrevolution/2026/03/what-is-economics-these-days.html which often punches above its weight, in part because it is far less insular. Accomplishment and impact across disciplines are alternatives to academic credentials as a way of making expertise legible.
Is not a particularly good description of what academia and the academic peer review process is actually doing in many fields, including academic philosophy
I don’t understand why you think this. I know academia has pathologies, sure, but it seems pretty clear — as a mechanistic claim, not an “outside view heuristic” — that academic philosophers are trained to scrutinize philosophical arguments. I don’t think you’ve really explained why I should believe that “accomplished and high impact” people have more experience with scrutinizing philosophical arguments than academic philosophers.
My experience taking philosophy classes at MIT was academic philosophers are trained very poorly at scrutinizing philosophical arguments. People adjacent to philosophy—logicians, mathematicians, linguists, (not physicists)—are generally better able to work through philosophical arguments. The first two because learning the language forces them to learn how to think argumentatively, the third because it deals with similar structure without the baggage introduced by academic philosophers.
For example, if I present the Grandfather Paradox to a professor in these four fields, I expect:
The logician would ask me for the axioms, and keep pushing until I admit one of them is, “your grandfather cannot die.”
The mathematician would say, “obviously you cannot kill your grandfather, otherwise you have a contradiction.”
The linguist would ask me what exactly I mean by grandfather—biological? has he frozen sperm? does he have children yet? a twin brother?—and conclude, “you can kill your grandfather, at least the person that word refers to in the mind of the time traveler.”
The philosopher would say, “oh that’s such an interesting thought experiment. I don’t know, can you? It doesn’t seem like you can’t, and yet that seems like it would create a contradiction.” Then they would try putting the paradox in premise-conclusion form, and two hours later conclude, “well many of these axioms and implications seem a little fishy, but I would have to say you can/cannot [equally likely] kill your grandfather”.
This is an incorrect characterization of the field. If you define a “relevant expert” as an academic who publishes exclusively in academic philosophy journals (which are mostly read, at best, by other academics), then 15 years ago that might have been a valid (if lame) argument from authority / status. But these days, the most accomplished and high impact philosophers do at least some of their work in industry (e.g. frontier AI labs and non-university-backed research orgs), and a significant chunk of them accept some flavor of FDT as true.
Who are the most accomplished and high impact philosophers who work in industry and adopt FDT?
“Adopt FDT” is probably too strong as a rephrasing; by “accept some flavor of FDT as true”, I intended to include anyone who one-boxes and / or cooperates in the prisoner’s dilemma because they disagree with you and academic-only philosophers on this:
Which is definitely a minority view among rationalists, and (I am pretty confident) a minority view among researchers and philosophers at frontier AI labs and similar. cf. https://www.lesswrong.com/posts/n6wajkE3Tpfn6sd5j/christiano-decision-theory-excerpt, particularly:
Of course there’s still a bunch of intra-rationalist and AI researcher disagreement on the specifics of FDT / UDT, e.g. a bunch of them probably disagree specifically because of updatelessness / EDT-with-tickle reasons, which are (debatably) not just “some flavor of FDT” as I said above.
IDK who exactly the most prominent people who have published specific thoughts on this are, but as a starting point the MacAskill post from 2019 that you cited got a bunch of substantive replies. I didn’t check all of their credentials / accomplishments and what they’re up to these days, but I suspect the real locus of our disagreement is more about the bounds of who qualifies as a philosopher / expert. I think “academic philosophy credentials” are not a good proxy for legible philosophy expertise (see sibling reply for more).
A big chunk of philosophers one-box. These people generally adopt evidential decision theory. They also cooperate in PD with twin. So no, FDT isn’t just the same as one boxing. If it was, then all EDTers would be FDTers.
I don’t think you should program an AI to follow CDT. This is because decision theories are theories of which actions are rational, not the dispositions that you want to have. So I agree with Christiano—this obviously can’t be the criterion for being a functional decision theorist.
Here’s one test: there is not a single person, to the best of my knowledge, anywhere in the world who adopts FDT and has a Ph.D in philosophy. This fact is surprising if it’s the right view.
False:
Insofar as we think we should defer to some extent to [group of people] on [topic], shouldn’t we defer to [group of people whose job it is to scrutinize arguments on that topic] more so than [group of people who “are most accomplished and high impact”]? What does the latter have to do with their expertise about decision theory?
As a starting point / outside view heuristic, maybe? But I think this:
> [group of people whose job it is to scrutinize arguments on that topic]
Is not a particularly good description of what academia and the academic peer review process is actually doing in many fields, including academic philosophy. Philosophy is not the worst field in terms of pathologies of academia, but IMO it is punching far below its weight given the intellectual horsepower and human capital it attracts. Compare to academic economics: https://marginalrevolution.com/marginalrevolution/2026/03/what-is-economics-these-days.html which often punches above its weight, in part because it is far less insular. Accomplishment and impact across disciplines are alternatives to academic credentials as a way of making expertise legible.
I don’t understand why you think this. I know academia has pathologies, sure, but it seems pretty clear — as a mechanistic claim, not an “outside view heuristic” — that academic philosophers are trained to scrutinize philosophical arguments. I don’t think you’ve really explained why I should believe that “accomplished and high impact” people have more experience with scrutinizing philosophical arguments than academic philosophers.
My experience taking philosophy classes at MIT was academic philosophers are trained very poorly at scrutinizing philosophical arguments. People adjacent to philosophy—logicians, mathematicians, linguists, (not physicists)—are generally better able to work through philosophical arguments. The first two because learning the language forces them to learn how to think argumentatively, the third because it deals with similar structure without the baggage introduced by academic philosophers.
For example, if I present the Grandfather Paradox to a professor in these four fields, I expect:
The logician would ask me for the axioms, and keep pushing until I admit one of them is, “your grandfather cannot die.”
The mathematician would say, “obviously you cannot kill your grandfather, otherwise you have a contradiction.”
The linguist would ask me what exactly I mean by grandfather—biological? has he frozen sperm? does he have children yet? a twin brother?—and conclude, “you can kill your grandfather, at least the person that word refers to in the mind of the time traveler.”
The philosopher would say, “oh that’s such an interesting thought experiment. I don’t know, can you? It doesn’t seem like you can’t, and yet that seems like it would create a contradiction.” Then they would try putting the paradox in premise-conclusion form, and two hours later conclude, “well many of these axioms and implications seem a little fishy, but I would have to say you can/cannot [equally likely] kill your grandfather”.