Irenaeus pointed to the public rule of faith, authoritatively articulated by the preaching of bishops and inculcated in Church practice, especially worship, as an authentic apostolic tradition by which to read Scripture truly against heresies. He classified as Scripture not only the Old Testament but most of the books now known as the New Testament, while excluding many works, a large number by Gnostics, that flourished in the 2nd century and claimed scriptural authority. Oftentimes, Irenaeus, as a student of Polycarp, who was a direct disciple of the Apostle John, believed that he was interpreting scriptures in the same hermeneutic as the Apostles. This connection to Jesus was important to Irenaeus because both he and the Gnostics based their arguments on Scripture. Irenaeus argued that since he could trace his authority to Jesus and the Gnostics could not, his interpretation of Scripture was correct. He also used "the Rule of Faith", a "proto-creed" with similarities to the Apostles' Creed, as a hermeneutical key to argue that his interpretation of Scripture was correct.