In this volume, two classical texts of legal theory (usul al-fiqh) are analysed. The authors of these works belonged to two schools of Shi'i jurisprudence: Yusuf al-Bahrani (d. 1186/1772) was a key figure in the Akhbari school, and his adversary, Muhammad Baqir al-Bihbahaani (d. 1206/1791-2) was credited with the revival of the Usuli school and the defeat of Akhbarism after Bahrani's death. Through a comparison of the two writers' theories, this work describes the major areas of dispute between the two schools, examining how their different epistemologies lead to different conceptions of the sources and interpretation of the Shari'a, God's law for humanity. This work will, then, be of interest to historians of Islamic thought generally, and Shi'i thought and Islamic legal theory, in particular.