89 We believe that when the Ecumenical Council comes to deal with the problems relating to the Church's activity in the modern world, it will give the doctrinal and practical rules needed for the proper conduct of our dialogue with our contemporaries. We believe too that in matters relating to the Church's actual apostolic mission and the many changing circumstances in which it is exercised, the supreme authority of the Church will in every instance determine wise, effective and clear aims, principles, and methods, so that a lively and effective dialogue may be assured and lasting.
Source: Ecclesiam Suam (Vatican.va)