The Book of Knowledge (Kitab al-ilm) is the foundation of the forty books of the Revival of the Religious Sciences (Ihya ulum al-din), Imam al-Ghazali’s magnum opus. In the Book of Knowledge, he defines knowledge, its relation to faith, theology, and jurisprudence. The book deals with the virtue of knowledge from both rational and traditional points of view. It elucidates the types of knowledge and the nature of people’s obligation to seek knowledge.