This is the first English translation of one of the most important treatises written during the late-Middle Ages in defense of converts from Judaism, favoring religious tolerance in the face of religious and racially motivated prejudice and violence. The book also includes a fresh Latin edition, drawing on all known manuscripts. The text was written in response to the actions of the "e;Old Christians"e; of Toledo against the "e;New Christians,"e; also called conversos, in 1449. A letter of Pope Nicholas V favouring the converts is included.