Which summarizes my confusion. If CDT is this clearly broken, why is it so discussed (and apparently defended, though I don’t actually know any defenders).
Dagon, I sympathize. CDT seems bonkers to me for the reasons you have pointed out. My guess is that academic philosophy has many people who support CDT for three main reasons, listed in increasing order of importance:
(1) Even within academic philosophy, many people aren’t super familiar with these arguments. They read about CDT vs. EDT, they read about a few puzzle cases, and they form an opinion and then move on—after all, there are lots of topics to specialize in, even in decision theory, and so if this debate doesn’t grip you you might not dig too deeply.
(2) Lots of people have pretty strong intuitions that CDT vindicates. E.g. iirc Newcomb’s Problem was originally invented to prove that EDT was silly (because, silly EDT, it would one-box, which is obviously stupid!) My introductory textbook to decision theory was an attempt to build for CDT an elegant mathematical foundation to rival the jeffrey-bolker axioms for EDT. And why do this? It said, basically, “EDT gives the wrong answer in Newcomb’s Problem and other problems, so we need to find a way to make some version of CDT mathematically respectable.”
(3) EDT has lots of problems too. Even hardcore LWer fans of EDT like Caspar Oesterheld admit as much, and even waver back and forth between EDT and CDT for this reason. And the various alternatives to EDT and CDT that have been thus far proposed also seem to have problems.
My introductory textbook to decision theory was an attempt to build for CDT an elegant mathematical foundation to rival the jeffrey-bolker axioms for EDT. And why do this? It said, basically, “EDT gives the wrong answer in Newcomb’s Problem and other problems, so we need to find a way to make some version of CDT mathematically respectable.”
Joyce’s Foundations of Causal Decision Theory, right? That was the book I bought to learn decision theory too. My focus was on anthropic reasoning instead of Newcomb’s problem at the time, so I just uncritically accepted the book’s contention that two-boxing is the rational thing to do. As a result, while trying to formulate my own decision theory, I had to come up with complicated ways to force it to two-box. It was only after reading Eliezer’s posts about Newcomb’s problem that I realized that if one-boxing is actually the right thing to do, the decision theory could be made much more elegant. (Too bad it turns out to still have a number of problems that we don’t know how to solve.)
Which summarizes my confusion. If CDT is this clearly broken, why is it so discussed (and apparently defended, though I don’t actually know any defenders).
Dagon, I sympathize. CDT seems bonkers to me for the reasons you have pointed out. My guess is that academic philosophy has many people who support CDT for three main reasons, listed in increasing order of importance:
(1) Even within academic philosophy, many people aren’t super familiar with these arguments. They read about CDT vs. EDT, they read about a few puzzle cases, and they form an opinion and then move on—after all, there are lots of topics to specialize in, even in decision theory, and so if this debate doesn’t grip you you might not dig too deeply.
(2) Lots of people have pretty strong intuitions that CDT vindicates. E.g. iirc Newcomb’s Problem was originally invented to prove that EDT was silly (because, silly EDT, it would one-box, which is obviously stupid!) My introductory textbook to decision theory was an attempt to build for CDT an elegant mathematical foundation to rival the jeffrey-bolker axioms for EDT. And why do this? It said, basically, “EDT gives the wrong answer in Newcomb’s Problem and other problems, so we need to find a way to make some version of CDT mathematically respectable.”
(3) EDT has lots of problems too. Even hardcore LWer fans of EDT like Caspar Oesterheld admit as much, and even waver back and forth between EDT and CDT for this reason. And the various alternatives to EDT and CDT that have been thus far proposed also seem to have problems.
Joyce’s Foundations of Causal Decision Theory, right? That was the book I bought to learn decision theory too. My focus was on anthropic reasoning instead of Newcomb’s problem at the time, so I just uncritically accepted the book’s contention that two-boxing is the rational thing to do. As a result, while trying to formulate my own decision theory, I had to come up with complicated ways to force it to two-box. It was only after reading Eliezer’s posts about Newcomb’s problem that I realized that if one-boxing is actually the right thing to do, the decision theory could be made much more elegant. (Too bad it turns out to still have a number of problems that we don’t know how to solve.)
Yep, that’s the one! :)