How is one to wade through the apparent welter of irreconcilable primary Islamic sources? What is one to do when faced with opposing practices of the Prophet (Sallallahu Alayhi Wa Sallam) on the same issue? When is a practice deemed necessary or recommended? These are some of the topics discussed in usul al-fiqh. Loosely translated as principles of Islamic jurisprudence, usul al-fiqh is the legal theory which underpins Islamic positive law and practical ethics. The book Usul ash-Shashi is an isagogic opuscule on legal theory according to the Hanafi School of Law. It is widely favoured and accepted in the darse niazmi syllabus of South Asian seminaries and their sister institutions outside of the Asian Subcontinent despite little being known of its author. The translation will appeal to a wide readership in particular to elementary students of Islamic law and to those that are interested in legal theory.