Ratzinger became a professor at the University of Bonn in 1959; his inaugural lecture was on "The God of Faith and the God of Philosophy." In 1963, he moved to the University of Münster. During this period, Ratzinger participated in the Second Vatican Council (1962–65). Ratzinger served as a peritus (theological consultant) to Josef Cardinal Frings of Cologne. He was viewed during the time of the Council as a reformer, cooperating with radical Modernist theologians like Hans Küng and Edward Schillebeeckx. Ratzinger became an admirer of Karl Rahner, a well-known academic theologian of the Nouvelle Théologie and a proponent of church reform.