 Arabic logic began to fragment in the fifteenth and sixteenth centuries and several centers developed. El-Rouyaheb identifies distinct Ottoman Turkish, Iranian, Indo-Muslim, North African, and Christian Arabic traditions. These developed independently of one other, and, according to El-Rouyaheb, it is the Ottoman Turkish tradition that is the most important up to the twentieth century. The basic themes outlined by Avicenna remained dominant in this tradition, however. 