Meeting moved to Arché seminar room, due to bank holiday.

We are very pleased that Aaron Cotnoir will be presenting a talk titled “Parts of Proper Classes”

Abstract: Set theory is plagued with problems of absolute generality: there is no set of all sets, no set of all ordinals, no set of all non-self-membered sets, etc. Collections that are ‘too big’ to be sets are typically called proper classes. But proper classes are philosophically puzzling in their own right. Classical mereology was invented by Lesniewski as an alternative to set theory that didn’t suffer from Russell’s paradox. Lesniewski’s programme in the foundations of mathematics failed, in part because classical mereology is far too weak to serve as an adequate alternative to set theory. I’ll argue, though, that classical mereology can serve as a adequate foundation for the theory of classes, and that a non-antisymmetric variant of mereology can do an even better job of answering the philosophical puzzles regarding proper classes.