The Problem of Negative Existentiality

The problem of negative existential. What Quine calls Plato's beard? Maybe one way to spell that out would be to say that there is a possible world somewhere containing Pegasus, only it isn't the actual world. But there might be other ways of spelling that out as well that don't involve possible worlds. If you think that there is Pegasus, only he doesn't exist. And so the dilemma here is how can we actually be speaking meaningfully or making meaningful statements about something that doesn't exist?"