Why “Philosophy in Islam”? Why not “Islamic Philosophy” or “Arabic Philosophy”? The simple answers to these questions and the far from simple consequences of those answers provide an entry into the rich world of ideas briefly explored in this chapter. The simple answer to the question “Why not 'Islamic Philosophy'?” is that not all philosophers in lands under Islamic rule in the Middle Ages were Muslim. It is easy to forget how diverse the empire of Islam was and, in particular, that it included numerous lively religious minorities. Among philosophers there were: Muslims, such as al-Farabi,Avicenna (Ibn Sina), andAverroes (Ibn Rushd), some of whom were Sunni, others Shiites or Ismaili, as the Brethren of Purity Christians, for instance Yahya Ibn ’Ady, a leading disciple of al-Farabi and a well-known Jacobite theologian Sabians, such as the physician Thabit ibn Qurra, a translator Mazdaeans or Zoroastrians, such as Mani al-Majusi Pagans, such as Abu Bakr al-Razi, the famous Rhazes, who denied the very possibility of revelation or prophecy, on the ground that it would favor a particular people and would therefore be incompatible with God’s justice Jews, such as Ibn Suwar, Halevy, Maimonides, etc. The great number and importance of Jewish philosophers, including those working in the Latin West after the Reconquista, call for a full chapter devoted to their thought (the chapter following this one), but they, as well as the other non-Muslims listed above, must be considered as participants in a single philosophical conversation carried on from the ninth through the thirteenth century and beyond.