This is the first full-length study of Vico's Diritto Universale to be written in English. This study places the work within the wider traditions of Roman legal scholarship and natural law, which Vico was confronting. Truth and Authority in Vico's Universal Law breaks new ground in the treatment of Aristotelian influences on Vico. It examines Vico's idea that a theory founded on the subjective right of the single individual cannot be the foundation of social relationships. This entails the investigation of Vico's refusal to endorse rationality as the basis of authority and political agreement conceived as "contract." It traces a continuity between the Diritto Universale and Vico's major work, the Scienza Nuova .