In the Habsburg lands "positive knowledge" served as the key framework of liberal science from the 1830s because it permitted its practitioners to trace ineluctable social-political progress. In the 1850s Mill's version of positivism was translated to the Austrian lands by the classicist Theodor Gomperz. In this chapter traces the rival varieties of positivism across scientific domains (the natural sciences, philology, philosophy, history, law). It demonstrates how Mill's model of inquiry was refashioned by Ernst Mach and Franz Brentano, by the Vienna Circle (Schlick, Carnap, Neurath), as well as by Hans Kelsen's critical-democratic legal positivism. The final section analyzes the fin de siècle shipwreck of positivism in conjunction with the collapse of Austrian liberalism whose vision of benign imperial rule, society, and scientific inquiry it had provided.