The classification of knowledge is a recurring theme in Islamic scholarship. Successive generations of Muslim scholars, from al-Kindi in the ninth century to Shah Waliallah of Delhi in the eighteenth century, have devoted considerable efforts to the exposition of this theme. The lives and the ideas of the three thinkers discussed in Classification of Knowledge in Islam - al-Farabi (870-950AD), al-Ghazzali (1058-1111AD) and Qutb al-Din al-Shirazi (1236-1311AD) - cover the pivotal period of Islamic history from the first flourishing of the philosophical sciences to the sacking of Baghdad by the Mongols. In addition, each of these three thinkers was either a founder or an eminent representative of a major intellectual school in Islam. Al-Farabi was the founder and one of the most prominent representatives of the mashsha'i (Peripatetic) school of philosopher-scientists. Al-Ghazzali is still recognised as the most famous theologian/sufi of Islam. Qutb al-Din al-Shirazi represents the ishraqi (Illuminationists) school of philosophy. Prof. Osman Bakar's Classification of Knowledge in Islam is the first work of its kind in the English language and is based on extensive scholarships and reference to the original texts.