US historian of religion. He wrote over 30 books, including the monumental 5-volume Christian Tradition (1971, 1974, 1978, 1984, 1989). His Riddle of Roman Catholicism (1959) sold many copies during the presidential campaign of John F Kennedy in 1960. He called for dialogue between Christianity and Judaism.
He was born in Akron, Ohio, descended from Eastern European ministers. Extremely precocious, he started to write at age two, entering high school at age nine. He earned his PhD at 22, and subsequently taught at Yale University from 1962, serving as dean of the Graduate School 1973–78. His 1992 Gifford lectures at the University of Aberdeen were published as Christianity and Classical Culture (1995).