The names of the famous Arabic philosophers Averroes and Avicenna, alongside those of Alkindi, Alfarabi, and Algazel, appear in countless philosophical writings of the Renaissance. These authors are well-known figures of the classical period of Arabic philosophy, which stretches from the ninth to the twelfth century ad. The history of Arabic philosophy began in the middle of the ninth century, when a substantial part of ancient Greek philosophy had become available in Arabic translations: almost the complete Aristotle, numerous Greek commentaries on Aristotle, and many Platonic and Neoplatonic sources. A major centre of intellectual activity was Baghdad, the new capital of the Abbasid caliphs. It was here that Alkindi (al-Kindī, d. after ad 870), the first important philosopher of Arabic culture, and the Aristotelian philosopher Alfarabi (al-Fārābī, d. 950/1) spent the greater part of their life. A major turning point in the history of Arabic philosophy was the activity of Avicenna (Ibn Sīnā, d. 1037), the court philosopher of various local rulers in Persia, who recast Aristotelian philosophy in a way that made it highly influential among Islamic theologians. The famous Baghdad theologian Algazel (al-Ghazālī, d. 1111) accepted much of Avicenna’s philosophy, but criticized it on central issues such as the eternity of the world. Averroes (Ibn Rushd, d. 1198), the Andalusian commentator on Aristotle, reacted to both Avicenna and Algazel: he censured Avicenna for deviating from Aristotle and criticized Algazel for misunderstanding the philosophical tradition.