The issue of the relationship between our cogitative abilities, in particular the ability of thinking about something that does not exist, and modal characteristics, in particular those featuring unactualized (im)possibilities, i.e., the ways the world might (not) have been, has always been very intricate.

In analytic philosophy, reflection on this matter has started by reviving an optimistic thesis traditionally ascribed to Hume, according to which conceivability entails possibility: if something is conceivable, then it is also possible. As Wittgenstein clearly suggests in the incipit of the Tractatus logico-philosophicus, where he says that that there is no room for conceptions of something impossible: