The apology of Aristides was written as a defence of the new Christian way of life against its many rivals and opponents, and details some of its leading ethical precepts. Long thought to have been lost, this early second-century work was rediscovered in a Syriac translation in 1889 in a seventh-century manuscript preserved in the monastery of St. Catherine on Mount Sinai. This volume contains not only the standard edition of the Syriac text with critical notes, but also the first English translation, and a study of surviving fragments in Greek, the original language of the apologia, which were subsequently identified in the 'Life of Barlaam and Josaphat' (an early Christian reworking of the life of Buddha).