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Lewis's empiricism

Last week, I gave a talk in Manchester at a (very nice) workshop on "David Lewis and His Place in the History of Analytic Philosophy". My talk was on "Lewis's empiricism". I've now written it up as a paper, since it got too long for a blog post.

The paper is really about hyperintensional epistemology. The question is how we can make sense of the kind of metaphysical enquiry Lewis was engaged in if we accept his models of knowledge and belief, which leave no room for substantive investigations into non-contingent matters.

From Sensor Variables to Phenomenal Facts

I wrote this short piece for a special issue of the Journal of Consciousness Studies on Chalmers's "The Meta-Problem of Consciousness" (2018). Much of my paper rehashes ideas from section 5 of my "Imaginary Foundations" paper, but here I try to present these ideas more simply and directly, without the Bayesian background.

How to serve two epistemic masters

In this 2018 paper, J. Dmitri Gallow shows that it is difficult to combine multiple deference principles. The argument is a little complicated, but the basic idea is surprisingly simple.

Suppose A and B are two weather forecasters. Let r be the proposition that it will rain tomorrow, let A=x be the proposition that A assigns probability x to r; similarly for B=x. Here are two deference principles you might like to follow:

Relativism and absolutism in deontic logic

Consider a world where eating doughnuts is illegal and where everyone thinks it is OK to torture animals for fun. Suppose Norman at w is eating doughnuts while torturing his pet kittens. Is he violating the laws? Is he doing something immoral?

In one sense, yes, in another, no. His doughnut eating violates the laws of w, but not the laws of our world. Conversely, his kitten torturing violates a moral code accepted at our world, but not a code accepted at w.

On Functional Decision Theory

I recently refereed Eliezer Yudkowsky and Nate Soares's "Functional Decision Theory" for a philosophy journal. My recommendation was to accept resubmission with major revisions, but since the article had already undergone a previous round of revisions and still had serious problems, the editors (understandably) decided to reject it. I normally don't publish my referee reports, but this time I'll make an exception because the authors are well-known figures from outside academia, and I want to explain why their account has a hard time gaining traction in academic philosophy. I also want to explain why I think their account is wrong, which is a separate point.

Duals of knowledge and belief

On the modal analysis of belief, 'S believes that p' is true iff p is true at all possible worlds compatible with S's belief state. So 'believes' is a necessity modal. One might expect there to be a dual possibility modal, a verb V such that 'S Vs that p' is true iff p is true at some worlds compatible with S's belief state. But there doesn't seem to be any such verb in English (or German). Why not?

What do we use if we want to say that something is compatible with someone's beliefs? Suppose at some worlds compatible with Betty's belief state, it is currently snowing. We could express this by "Betty does not believe that it is not snowing". But (for some reason) that's really hard to parse.

Gibbard and Jackson on the probability of conditionals

Gibbard's 1981 paper "Two recent theories of conditionals" contains a famous passage about a poker game on a riverboat.

Sly Pete and Mr. Stone are playing poker on a Mississippi riverboat. It is now up to Pete to call or fold. My henchman Zack sees Stone's hand, which is quite good, and signals its content to Pete. My henchman Jack sees both hands, and sees that Pete's hand is rather low, so that Stone's is the winning hand. At this point, the room is cleared. A few minutes later, Zack slips me a note which says "If Pete called, he won," and Jack slips me a note which says "If Pete called, he lost." I know that these notes both come from my trusted henchmen, but do not know which of them sent which note. I conclude that Pete folded.

One puzzle raised by this scenario is that it seems perfectly appropriate for Zack and Jack to assert the relevant conditionals, and neither Zack nor Jack has any false information. So it seems that the conditionals should both be true. But then we'd have to deny that 'if p then q' and 'if p then not-q' are contrary.

One-boxing and objective consequentialism

I've been reading about objective consequentialism lately. It's interesting how pervasive and natural the use of counterfactuals is in this context: what an agent ought to do, people say, is whichever available act would lead to the best outcome (if it were chosen). Nobody thinks that an agent ought to choose whichever act will lead to the best outcome (if it is chosen). The reason is clear: the indicative conditional is information-relative, but the 'ought' of objective consequentialism is not supposed to be information-relative. (That's the point of objective consequentialism.) The 'ought' of objective consequentialism is supposed to take into account all facts, known and unknown. But while it makes perfect sense to ask what would happen under condition C given the totality of facts @, even if @ does not imply C, it arguably makes no sense to ask what will happen under condition C given @, if @ does not imply C.

The probability that if A then B

It has often been pointed out that the probability of an indicative conditional 'if A then B' seems to equal the corresponding conditional probability P(B/A). Similarly, the probability of a subjunctive conditional 'if A were the case then B would be the case' seems to equal the corresponding subjunctive conditional probability P(B//A). Trying to come up with a semantics of conditionals that validates these equalities proves tricky. Nonetheless, people keep trying, buying into all sorts of crazy ideas to make the equalities come out true.

Spelling out a Dutch Book argument

Dutch Book arguments are often used to justify various epistemic norms – in particular, that credences should obey the probability axioms and that they should evolve by condionalization. Roughly speaking, the argument is that if someone were to violate these norms, then they would be prepared to accept bets which amount to a guaranteed loss, and that seems irrational.

But it's hard to spell out how exactly the argument is meant to go. In fact, I'm not aware of any satisfactory statement. Here's my attempt.

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