Unlike conventional interpretations of Kant's Rechtslehre, Rainer Friedrich demonstrates that Kant does not derive the necessity of a state of public law from natural property law. Rather, the innate human right of liberty forms the subjective legal basis of the state.

The close textual analysis both consults the preparatory studies to the doctrine of law and virtue and Kant's relevant lectures and considers contemporary commentaries. The study emphasizes the systematicity of duty underlying the Rechtslehre, Kant's doctrine of subjective rights, the doctrine of original acquisition and the significance of the general will for private law, together with the transition from private to public law. Rainer Friedrich provides a coherent historically and systematically arranged reconstruction of Kant's rationality of law.