The encyclical on the condition of the Catholic missions, and especially on Africa at a moment of rapid social and political change. Pius XII sets out the missionary responsibility that belongs to every bishop and not only to those who govern mission territories: the whole Church is answerable for the whole Church, and dioceses rich in clergy are asked to lend priests, for a fixed term, to the young Churches that lack them — the practice from which such priests came to be known as Fidei donum priests. The letter also urges the raising up and thorough formation of a local clergy, religious and lay apostolate; the support of Catholic schools, catechists and charitable works; prayer and sacrifice for the missions; and generous cooperation with the pontifical mission societies, so that the faith which is itself God's gift may be handed on by those who have received it.