ʿAzīz Nasafī (d. 13th century) is a prime example of the vibrant intellectual life of the Persianate Mongol World. While he is often celebrated as a mystic or Sufi, little attention has been paid to his engagement with scientific ideas. A practicing physician, Nasafī had a thorough knowledge of the various branches of science, and he constantly incorporated them into his oeuvre. He particularly used medicine, astrology, and lettrism in his works and drew upon them to articulate his ideas. This presentation looks at ways that he employs these three branches of knowledge to resolve human conflicts and cultivate perfection, serving as primary scientific-cosmopolitan means to achieve universal harmony and peace. Nasafī's reliance on these scientific-occult modes of tajriba characterize his overarching project of universal peace or sulḥ bā hama, paving the way for the early modern Mughal imperialist legacy. I further argue that Nasafī’s scientific cosmopolitanism is best understood with respect to the emergence of Mongol Imperialism and the ensuing radical socio-political changes in the Islamic world.