The Trouble with Possible Worlds

In what sense or senses, if any, should we admit that “there are” possible but nonexistent beings or possible but nonactual worlds? Sources of motivation for some such admission are powerful and various. By positing nonexistent individuals, it seems, we may understand true negative existentials and accommodate the intentionality of certain mental entities. By positing nonactual worlds or states of affairs, we may achieve our familiar but still remarkable reduction of the alethic modalities to quantifiers,1 formulate truth-conditional semantics for prepositional attitudes and hosts of other troublesome constructions, display the otherwise mysterious connections between Fregean senses and linguistic meaning,2 illuminate the pragmatics of counterfactuals and other conditionals, and provide a rigorous format for the theoretical study of decision making.3 Even ordinary ways of speaking encourage us to reify nonexistent possibles at every turn.4