This article explores how the World Bank’s engagement with governance reform has sparked a practice of measuring, ranking and diagnosing countries based on an epistemically constructed ideal-type of the modern state. With Foucault, I define this praxis of normalisation as a ‘transnational discipline of diagnosis’. The contribution of the article is both empirical and doctrinal. On an empirical level, it weaves together an innovative assemblage of three different technologies in the Bank’s epistemic governance praxis: the axiomatic dimension (World Development Reports); the statistical dimension (Worldwide Governance Indicators) and the diagnostic dimension (Systematic Country Diagnostics). On a doctrinal level, drawing on critical sociology and performativity theory, the article categorises this epistemic praxis as a world-making socio-political enterprise. It thereby rejects both the categorisation of epistemic power as a mode of public authority (to be integrated in a public law framework), as well as the respresentationalist idioms that inform ideology critique.