Abstract

In the nineteenth century, astronomers thought that a planet between Mercury and the Sun was causing perturbations in the orbit of Mercury, and they introduced ‘Vulcan’ as a name for such a planet. But they were wrong: there was, and is, no intra-Mercurial planet. Still, these astronomers went around saying things like (2) Vulcan is a planet between Mercury and the Sun. Some philosophers think that, when nineteenth-century astronomers were theorizing about an intra-Mercurial planet, they created a hypothetical planet.