This article offers an assessment of the ethical status of territorial borders, arguing for a partial defence of their role in international relations. Utilising the English School as one way such a defence has been developed, it assesses pluralist and solidarist arguments, suggesting both are flawed. The article develops a notion of territorial borders as contributing to the value of tolerating difference in international relations, and that this is an ethically desirable thing to do. It doing so it utilises the political theory of Hannah Arendt as an alternative to more common, if usually implicit, liberal understandings.