The Logic and Metaphysics Workshop will meet on April 9th from 4:15-6:15 in room 3309 of the CUNY Graduate Center for a talk by Greg Restall (Melbourne).

**Title**: Isomorphisms in a Category of Proofs

**Abstract**: In this talk, I show how a category of classical proofs can give rise to three different hyperintensional notions of sameness of content. One of these notions is very fine-grained, going so far as to distinguish p and p∧p, while identifying other distinct pairs of formulas, such as p∧q and q∧p; p and ¬¬p; or ¬(p∧q) and ¬p∨¬q. Another relation is more coarsely grained, and gives the same account of identity of content as equivalence in Angell’s logic of analytic containment. A third notion of sameness of content is defined, which is intermediate between Angell’s and Parry’s logics of analytic containment. Along the way we show how purely classical proof theory gives resources to define hyperintensional distinctions thought to be the domain of properly non-classical logics.

**Slides/Handout**: for those interested, the slides and handout for this talk will be made available for advance reading here.