Without doubt Arabic is the most important language ofIslamic philosophy and even the Persians, who have produced the largest number of Islamic philosophers, have written mostly in Arabic and produced some ofthe best known classics ofIslamic philosophy in the Arabic language, such as the Shifo' and the Maqii~id al-faliisifah. But it is equally true that Islamic philosophical texts in Persian constitute an important corpus without whose study the understanding of later Islamic philosophy as it developed in Persia and the Indo-Pakistani subcontinent would be impossible. Moreover, even in the case of some of the earlier figures who wrote in both Arabic and Persian, men like Ibn Sinii and GhazziilI, the totality of their message cannot be understood without taking into consideration their Persian writings. There are even figures in both the earlier and the later centuries of Islamic history who wrote mostly or completely in Persian, such as Nii~ir-i Khusraw and Afq.al aI-Din KiishiinI, and who are usually left out of consideration in most of the general histories ofIslamic philosophy precisely because of the language in which they expressed their ideas. Of course Turkish and Urdu are also of some importance for certain philosophical texts written during the past two or three centuries, but the use of Persian goes back over a thousand years and the Persian language must be considered along with Arabic as a main language in which the Islamic intellectual sciences were expressed in Persia itself as well as in the subcontinent and even to a certain extent in the Turkish world.