David Chalmers claims that if something is conceivable; then that entails that it's also – metaphysically - possible. The problem with this is that Chalmers distinguishes conceivability from imagination. That is, even if we can't construct mental images of nothing (or nothingness), we can still conceive of nothing (or nothingness). I, for one, can't even conceive of nothing (or nothingness).
In addition I have no intuitions about nothing or even about the idea of nothing.