 Impossible Ways: just as possible worlds are often introduced intuitively by characterising them as ways things could have been, so are impossible worlds often characterized as ways things could not have been. The initial insight is that not everything is possible, that is, some things just (absolutely) cannot happen. Anything that just can’t happen must be an absolute impossibility; and these ways the world just couldn’t be are impossible worlds (see e.g. Salmon 1984; Yagisawa 1988; Restall 1997; Beall &amp; van Fraassen 2003). 