This chapter considers the emergence of one of the main vehicles for the diffusion of new ideas of religiosity, literary Turkish. In contrast to previous studies which have claimed the emergence of Turkish as an expression of a proto-nationalism, this chapter argues that the emergence of Turkish must be seen against the twin background of the interest of Sufis, especially Jalal al-Din Rumi and his circle, in multi-lingual communication, and the new political circumstances thrown up by the Mongol invasions. Turkish is initially used extensively only for literary works in new cultural centres emerging in his period – the Mongol garrison town of Kırşehir, and the Turkmen principalities of the coastal peripheries. In the old Seljuq urban centres of Anatolia, Konya, Kayseri and Sivas, Persian remained the dominant if not the only form of literary language into the fifteenth century. Turkish thus seems to have been a medium not just to communicate with an audience unversed in Persian, but an expression of political and religious aspirations.