53 Whoever refuses to admit these principles, and hence to apply them to education, must necessarily deny that Christ has founded His Church for the eternal salvation of mankind, and maintain instead that civil society and the State are not subject to God and to His law, natural and divine. Such a doctrine is manifestly impious, contrary to right reason, and, especially in this matter of education, extremely harmful to the proper training of youth, and disastrous as well for civil society as for the well-being of all mankind. On the other hand from the application of these principles, there inevitably result immense advantages for the right formation of citizens. This is abundantly proved by the history of every age. Tertullian in his Apologeticus could throw down a challenge to the enemies of the Church in the early days of Christianity, just as St. Augustine did in his; and we today can repeat with him: Let those who declare the teaching of Christ to be opposed to the welfare of the State, furnish us with an army of soldiers such as Christ says soldiers ought to be; let them give us subjects, husbands, wives, parents, children, masters, servants, kings, judges, taxpayers and tax gatherers who live up to the teachings of Christ; and then let them dare assert that Christian doctrine is harmful to the State. Rather let them not hesitate one moment to acclaim that doctrine, rightly observed, the greatest safeguard of the State.
Source: Divini Illius Magistri (Vatican.va)