Wilhelm von Humboldt's legal philosophy is much less familiar than his philosophy of language or even his role as an educational reformer. For this purpose the author examines Humboldt's "Ideas on an attempt to determine the limits of the effectiveness of the state". This early work, which is central for political liberalism, was created in an exchange of ideas with Friedrich Schiller and had a substantial effect on John Stuart Mill's essay "On Liberty". The author attempts a legal-philosophical examination of Humboldt's ideas that is linked with a critical tracing of the Anglo-American origins and reception (together with Mill, above all Adam Smith, Rawls, Nozick and Buchanan).