Esperantist radical Eugène Lanti (1879–1947) anticipated a total ‘unification’ of humankind, envisioning that national, linguistic, and social differences would soon give way to a global, stateless, monolingual, postcapitalist utopia. This vision was grounded in Lanti's understanding of history as teleological progress toward increased rationality, social integration, and demythologization, as well as in his cosmopolitan reinterpretation of the social utility of Esperanto, which prioritised anti-nationalism, revolutionary tactics, and class-struggle over humanism and language rights. Lanti's linguistic–political thought is, consequently, an enticing and a reflexively potent example of a non-canonical approach to linguistic community, progress, and radical equality. A critical reading of it – as is laid out here – casts light on some of the tensions immanent in any linguistic universalism.