The Pope: A Discussion of the Roman Primacy

It is most important that future shepherds and priests should have mastered a theology that has been carefully worked out in this way and not polemically, especially with regard to those aspects which concern the relations of separated brethren with the Catholic Church.

This importance is the greater because the instruction and spiritual formation of the faithful and of religious depends so largely on the formation which their priests have received.

Moreover, Catholics engaged in missionary work in the same territories as other Christians ought to know, particularly in these times, the problems and the benefits in their apostolate which derive from the ecumenical movement.

 The way and method in which the Catholic faith is expressed should never become an obstacle to dialogue with our brethren. It is, of course, essential that the doctrine should be clearly presented in its entirety. Nothing is so foreign to the spirit of ecumenism as a false irenicism, in which the purity of Catholic doctrine suffers loss and its genuine and certain meaning is clouded.

At the same time, the Catholic faith must be explained more profoundly and precisely, in such a way and in such terms as our separated brethren can also really understand.

Moreover, in ecumenical dialogue, Catholic theologians standing fast by the teaching of the Church and investigating the divine mysteries with the separated brethren must proceed with love for the truth, with charity, and with humility. When comparing doctrines with one another, they should remember that in Catholic doctrine there exists a "hierarchy" of truths, since they vary in their relation to the fundamental Christian faith. Thus the way will be opened by which through fraternal rivalry all will be stirred to a deeper understanding and a clearer presentation of the unfathomable riches of Christ. (Vatican II, Unitatis Redintegratio)