First published in 1924, this volume contains the Donnellan lectures given by Francis Crawford Burkitt (1864-1935) at Trinity College Dublin in June 1923. Their subject is Manichaeism, a dualistic form of Christianity that thrived during the fourth and fifth centuries in Central Asia. Burkitt focuses especially on the discovery of fragments of Manichaean literary texts in Chinese Turkestan, near the Siberian border, early in the twentieth century. The first lecture introduces the history of the Manichees and reviews the sources of information available about them. The second discusses the Manichaean view of Jesus, Manichaean church organisation and Manichaean eschatology. The third analyses the influences behind Manichaean thought and teaching, including the important influences of Marcion and Saint Augustine. Burkitt's lectures were influential in publicising the new finds of Manichaean manuscript fragments, and remain an important resource for those studying heterodox movements in early Christianity.