In ninth-century Iran, a Zoroastrian scholar named Mardan-Farrukh watched the religions of his age compete for people's hearts — and found that doubt had reached his own. His answer was the Shikand-Gumanig Vizar, 'The Doubt-Dispelling Explanation,' a work of searching, often daring rational argument that remains a masterpiece of world theology. Written in clear, forceful Pahlavi, it takes up Islam, Christianity, Manichaeism, and Judaism one by one, asks whether their claims can stand the test of reason, and then turns to the deepest question of all: why does evil exist in a world a good God created? Mardan-Farrukh's reply — a defence of Zoroastrian dualism built on the freedom of the will — speaks as forcefully today as it did twelve centuries ago. This new edition renders his classic into warm, accessible present-day English, faithful to the meaning and spirit of the original. Part of The World Scriptures Library.