Although today associated exclusively with Islam, Iran has in fact played an unparalleled role within all the world religions, injecting Iranian ideas into the Jewish, Buddhist, Christian, and Manichaean traditions of the merchants who passed along the Silk Roads. This concise and readable introduction explores the manner in which Persian culture has interacted with and transformed each world faith, from the migration of the Israelites to Iran thousands of years ago, to the influence of Iranian notions on Mahayana Buddhism and Christian thought. The author also considers Iran's role in shaping the Muslim world, not only in the Middle East but also in South Asia, in an evocative and informative journey through the spiritual heritage of an ancient and influential region.