What, if anything, are possible worlds? And are there in fact possible worlds? I will argue that if there are possible worlds, then they may as well be certain propositions: if anything plays the theoretical role of possible worlds, then certain propositions do so, and we can translate any statement about possible worlds into an equivalent statement about these propositions. Further, I will argue that there are in fact certain propositions which play the theoretical role of worlds. These arguments depend on relatively strong modal background principles, including the non-contingency of possibility, the non-contingency of existence, and the identity of strictly equivalent propositions. To what extent similar arguments can be given without some of these assumptions is left open here. But for those who are happy to make these assumptions, it shows that reference to possible worlds in philosophical theorizing is unproblematic.
After the talks all are invited to socialise and continue discussion over drinks in the Ryle Room. If you would like to join for dinner after the drinks reception, please email firstname.lastname@example.org.