Pagels completed her Ph.D. in 1970, and joined the faculty at Barnard College. She headed its Department of Religion from 1974 until she moved to Princeton in 1982. In 1975, after studying the Pauline Epistles and comparing them to Gnosticism and the early Church, Pagels wrote the book, "The Gnostic Paul" which argues that Paul the Apostle was a source for Gnosticism and hypothesizes that Paul's influence on the direction of the early Christian church was great enough to inspire the creation of pseudonymous writings such as the Pastoral Epistles (First and Second Timothy and Titus), in order to make it appear that Paul was anti-Gnostic.