Today began the 1st Synthese Annual Conference, Between Intuition and Logic: David Lewis and the Future of Formal Philosophy, which was hosted at the Honorary Niels Bohr Mansion in Copenhagen and organized by Johan van Benthem, Vincent Hendricks and John Symons.
John Collins started things off with his paper "Formal and Informal Models of Belief", in which he embraced a Lewisian theory of knowledge:
if S knows that X, then there is no uneliminated possibility that is very close to actuality and in which X is false.He argued, among other things, that the threat of skepticism is not as ubiquitous as Vogel and Hawthorne suggest. The statistical information that n number of otherwise healthy people die of a heart attack is not enough to make the world in which i die of a heart attack very close to the actual world. That's because people don't just die of heart attacks if absolutely nothing is medically wrong with them. Since the actual world is not one where unbenownst to me there is something wrong with me, there is no very close world where I am one of the unlucky few to die in this way. So, my original ordinary knowledge claim about where I'll be tomorrow still stands. Of course, if it turns out that unbenownst to me and my doctors there is something medical wrong with my heart, then my ordinary knowledge claim falters.
Allesandro Torza gave the most formal of the talks thus far, titled "How to Lewis a Kripke-Hintikka". He argued that BL (i.e., [quantifier] independence friendly modal logic) is more expressive than QML (quantified modal logic); there are modal notions (e.g., the notion of rigidity for general terms) that can be expressed by BL but not by QML. However, this portion of BL cannot be translated into counterpart theory, and so, there is reason to doubt that counterpart theory is adequate to model our modal intuitions.
Brit and I gave a version of our paper "Remarks on Counterpossibles", in which we motivate and defend a modified version of Daniel Nolan's impossible worlds account of counterpossible conditionals.
Laurie Paul argued that the trumping examples, which have forced Lewis to give up his old theory of causation (see Schaffer's famous paper) do not obviously show what they were intended to show. The thrust of the objection was that until we clarify what it is to "interrupt a causal process", it is unclear how to interpret the trumping examples. The military handbook tells us that a Major's orders trump the Sgt.'s orders, but how do we get from there to a case of *causal* trumping? Merlin's (and not Morgana's) spell is stipulated to be the consequential of the two spells. But how do we get from there to Merlin's, but not Morgana's, spell caused the outcome?