Recent theorizing about cosmopolitanism has emphasized the need to embrace diversity as a constituent element informing the shared value of cosmopolitanism. This development suggests the need for an alternative genealogy from received accounts which typically trace cosmopolitanism from the Stoics through Kant, on the premise of moral continuities and consensus. My chapter explores the work of John Locke and his engagement with scepticism as a different way of encountering diversity with implications for a reimagined cosmopolitanism. But Locke’s inheritance is not straightforward and presents as many dilemmas as solutions to the challenge of reconciling difference with universal commitments. His acceptance, at some level, of diversity is not the prelude to an expression of human solidarity, framed around a nascent cosmopolitan ideal. Locke’s ultimate pessimism on these matters is a reminder of the difficulties involved in the contemporary project of accommodating divergent philosophical forces.