Scientific discoveries about Pluto and the rest of the universe led scientists to question Pluto’s status and ultimately to strip Pluto of its standing among planets. Neil deGrasse Tyson’s The Pluto Files masterfully weaves together the empirical, conceptual, and cultural questions surrounding Pluto’s demotion. The problem, for scientists and spectators alike, was this: there was no scientific definition of planet. This review systematizes the Pluto puzzle presented in the book and reveals its relevance for law. The questions presented by The Pluto Files – how man relates to the world, how man understands its conceptual categories, and how man should create distinctions along a continuum – are as relevant for the legal theorizing on Earth as they are for scientists’ understandings of space.