There were tax exemptions for religious figures and, to some extent, teachers and doctors. The Mongol Empire practiced religious tolerance because Mongol tradition had long held that religion was a personal concept, and not subject to law or interference.[citation needed] Sometime before the rise of Genghis Khan, Ong Khan, his mentor and eventual rival, had converted to Nestorian Christianity. Various Mongol tribes were Shamanist, Buddhist or Christian. Religious tolerance was thus a well established concept on the Asian steppe.