Abstract: The modal theory that David Lewis defended in On the Plurality of Worlds (Blackwell, 1986) is criticized. According to Lewis, to say that John Kerry might have won the 2004 presidential election is to say that someone very similar to Kerry does win his presidential election in a parallel universe (in an alternative “possible world”). This theory is indicative of a serious misunderstanding of such modal expressions as ‘possibly’ and ‘necessarily’, which are concerned not with any goings on in parallel universes but with what might have been. One need not disbelieve in possible worlds to recognize that they are not parallel universes.

Keywords: Lewis, modality, necessity, possibility,