Research Professor of Theology at Notre Dame and prolific author of books and pamphlets.

Born 20 January 1893 in Peoria, Illinois, John A. O'Brien attended St. Patrick School, the Spalding Institute, Holy Cross College (Worcester, Massachusetts), and St. Viator's College (Bourbonnais, Illinois). Bishop Edmund M. Dunne ordained him as a priest of the Diocese of Peoria and he celebrated his first Mass 18 June 1916. He served as chaplain for the Catholic students at the University of Illinois and earned a Ph.D. in psychology there. He started the Newman Foundation at the University of Illinois. He began his career as an author of Catholic books by organizing symposia (Catholics and Scholarship and The White Harvest) and writing about Evolution and Religion. In 1938 he published a book about Catholicism called The Faith of Millions which became a best seller (200,000 copies by 1945), was reprinted in 27 editions, and was translated into 10 languages. He remained at the University of Illinois for twenty-two years. In 1939 he spent a year at Oxford University and produced a book about communism, Thunder from the Left.

For the rest of his life he taught, and wrote, at the University of Notre Dame. Father O'Brien believed that Catholics ought to work actively to convert others to the Catholic faith; he participated in crusades to that end, organized campaigns in 50 American dioceses, spent his summers preaching in the streets of southern cities, published articles in popular magazines, and wrote pamphlets to promote missionary efforts and explain the doctrines of the Catholic Church. He continued to consider issues involving conflicts of secular and Catholic beliefs -- anti-Catholicism, birth and population control, priestly celibacy, communism, evolution, science, sex education -- and participated in friendly discussions with Protestants, Jews, Masons, and other non-Catholic groups. He wrote 45 books and hundreds of pamphlets and articles. In 1973, the University of Notre Dame awarded him the Laetare Medal. He died 18 April 1980 in South Bend, Indiana.