As the Ottoman Empire expanded into three continents throughout the fi fteenth century, the encounter with the “other” became a generalized condition of governing the empire. From the moment of its conquest by the Ottomans and their realization that governing Constantinople would involve dealing with already constituted social groups, Istanbul has always had to deal with negotiating differences among groups. When Constantinople was conquered in 1453, it was almost deserted. As is well known, Ottomans began repopulating Istanbul by transferring people from other conquered territories such as the Peloponnesian Salonika (modern Thessalonica) and the Greek islands. By about 1480 the population rose to between sixty thousand and seventy thousand (Inalcik). While Hagia Sophia and other Byzantine churches were transformed into mosques, the Greek patriarchate was retained and was moved to the Church of the Pammakaristos Virgin (Mosque of Fethiye), later to fi nd a permanent home in the Fener quarter. The capital of the Ottoman Empire was transferred to Constantinople from Adrianople (Edirne) in 1457. Within a century, Konstantiniye (as Ottomans called the city for a long time) was transformed into a “cosmopolitan” imperial city with inhabitants drawn from all corners of the empire and negotiating their differences, inventing along the way various legal, political, social, and cultural institutions with which such negotiations took place. I place the term cosmopolitan in quotation marks to indicate that I will increasingly turn critical toward the concept understood simply as presence of multiplicity, diversity, and plurality in a given space (Zubaida, “Cosmopolitanism and the Middle East”). By contrast, I will work toward a conception of cosmopolitanism as an ethic enabling and instituting practices of negotiation of differences without either reducing them or effacing such differences.