Keith Pecklers, SJ, Gasson Chair, describes 50 years of historical background, including discussions within the Vatican, that culminated in major liturgical changes approved in 1963. Fr. Pecklers is a professor of liturgy at the Pontifical Liturgical Institute of Rome and author of several books including The Unread Vision: The Liturgical Movement in the United States of America: 1926-1955 (The Liturgical Press, 1998) and Liturgy in a Postmodern World (Continuum International Publishing Group, 2006).