In early Islam learning was seen as a religious duty equivalent to an act of worship. This led to minute studies of the Quran, the collection of hadiths or traditions of other sayings of the Prophet, and the compilation of a detailed corpus of legal precedent by the ulama, scholars. From the ninth century onwards muslim scholars also translated and studied Greek works in a wide range of subjects. The Sufis sought direct knowledge of God by personal experience. These two trends were largely reconciled by Al-Ghazzali, d.1111. In the modern period several reform movements have arisen to meet the challenge of western knowledge and dominance.