Evangelii Nuntiandi §54

54. Nevertheless the Church does not feel dispensed from paving unflagging attention also to those who have received the faith and who have been in contact with the Gospel often for generations. Thus she seeks to deepen, consolidate, nourish and make ever more mature the faith of those who are already called the faithful or believers, in order that they may be so still more.

This faith is nearly always today exposed to secularism, even to militant atheism. It is a faith exposed to trials and threats, and even more, a faith besieged and actively opposed. It runs the risk of perishing from suffocation or starvation if it is not fed and sustained each day. To evangelize must therefore very often be to give this necessary food and sustenance to the faith of believers, especially through a catechesis full of Gospel vitality and in a language suited to people and circumstances.

The Church also has a lively solicitude for the Christians who are not in full communion with her. While preparing with them the unity willed by Christ, and precisely in order to realize unity in truth, she has the consciousness that she would be gravely lacking in her duty if she did not give witness before them of the fullness of the revelation whose deposit she guards.