Professor Joseph Cullen Ayer (Jr) (1866-1944) was the American author of A Source Book for Ancient Church History (1913). He was a Professor of Ecclesiastical History in the Divinity School of the Protestant Episcopal Church in Philadelphia. The value of the source-book has long been recognized in the teaching of general history. In ecclesiastical history quite as much use can be made of the same aid in instruction. It is hoped that the present book may supply a want increasingly felt by teachers employing modern methods in teaching ecclesiastical history. It has grown out of classroom work, and is addressed primarily to those who are teaching and studying the history of the Christian Church in universities and seminaries. But it is hoped that it may serve the constantly increasing number interested in the early history of Christianity.