Peritus (Latin for "expert") is the title given to Roman Catholic theologians who are present to give advice at an ecumenical council. At the most recent council, the Second Vatican Council, some periti (the plural form) accompanied individual bishops or groups of bishops from various countries. Others were formally appointed as advisers to the whole Council. John Henry Newman refused an invitation to be a peritus at the First Vatican Council. Fr. Joseph Ratzinger—the future Pope Benedict XVI—served as peritus to Cardinal Josef Frings, Archbishop of Cologne, Germany, while Hans Küng was a peritus for the Council, rather than for an individual Bishop. The influential German theologian Father Karl Rahner S.J. served as peritus to Cardinal Franz König of Vienna. Cardinal Yves Congar, O.P. served as a consultant to the Second Vatican Council upon the invitation of Pope John XXIII, but was hired as personal and expert theologian (peritus) at the council to Bishop Jean-Julien Weber of Strasbourg which allowed him to attend all the general sessions and to take part in the discussions of any conciliar commission to which he was invited by one of its members.