16 It is not only the evangelical content of the doctrine proclaimed by Saints Cyril and Methodius that merits particular emphasis. Also very expressive and instructive for the Church today is the catcehetic and pastoral method that they applied in their apostolic activity among the peoples who had not yet heard the Sacred Mysteries celebrated in their native language, nor heard the word of God proclaimed in a way that completely fitted their own mentality and respected the actual conditions of their own life. We know that the Second Vatican Council, twenty years ago, had as one of its principal tasks that of reawakening the self-awareness of the Church and, through her interior renewal, of impressing upon her a fresh missionary impulse for the proclamation of the eternal message of salvation, peace and mutual concord among peoples and nations, beyond all the frontiers that yet divide our planet, which is intended by the will of God the Creator and Redeemer to be the common dwelling for all humanity. The dangers that in our times are accumulating over our world cannot make us forget the prophetic insight of Pope John XXIII, who convoked the Council with the intent and the conviction that it would be capable of preparing and initiating a period of springtime and rebirth in the life of the Church. And, among its statements on the subject of universality, the same Council included the following: "All men are called to belong to the new People of God. Wherefore this People, while remaining one and unique, is to be spread throughout the whole world and must exist in all ages, so that the purpose of God's will may be fulfilled. In the beginning God made human nature one. After his children were scattered, he decreed that they should at length be unified again (cf. Jn 11:52)... The Church or People of God takes nothing away from the temporal welfare of any people by establishing that kingdom. Rather does she foster and take to herself, insofar as they are good, the abilities, resources, and customs of each people. Taking them to herself she purifies, strengthens, and enobles them... This characteristic of universality which adorns the People of God is a gift from the Lord himself... In virtue of this catholicity each individual part of the Church contributes through its special gifts to the good of the other parts and of the whole Church. Thus through the common sharing of gifts and through the common effort to attain fullness in unity, the whole and each of its parts receive increase".
Source: Slavorum Apostoli (Vatican.va)