The invaluable legacy of the Household [Ahl al-Bayt] of the Prophet (a), as preserved by their followers, is a comprehensive school of thought that embraces all branches of Islamic knowledge. This school has produced many brilliant scholars who have drawn inspiration from this rich and pure resource. It has given many scholars to the ummah [Muslim community] who, following in the footsteps of Imāms of the Prophet’s Household (a), have done their best to clear up the doubts raised by various creeds and currents within and without Muslim society and to answer their questions. Throughout the past centuries, they have given well-reasoned answers and clarifications concerning these questions and doubts. Al-Sayyid Hasan al-Sadr is an erudite scholar who, with authority discusses the Islamic and Arabic sciences, the factors responsible for their emergence and the various stages of their development throughout Shi'a sources.