Four future popes took part in the council 's opening session : Cardinal Giovanni Battista Montini , who on succeeding Pope John XXIII took the name of Paul VI ; Bishop Albino Luciani , the future Pope John Paul I ; Bishop Karol WojtyÅ a , who became Pope John Paul II . Father Joseph Ratzinger , who was only 35 at the time , was there as a theological consultant . Of those that took part in the council 's opening session , four have become pontiffs to date : Cardinal Giovanni Battista Montini , who on succeeding Pope John XXIII took the name of Paul VI ; Bishop Albino Luciani , the future Pope John Paul I ; Bishop Karol WojtyÅ a , who became Pope John Paul II ; and Father Joseph Ratzinger , present as a theological consultant , who became Pope Benedict XVI .