Arcanum, an Encyclical Letter on Christian marriage, issued February 10, 1880, by Leo XIII. Its scope is to show that, since family life is the germ of society, and marriage is the basis of family life, the healthy condition of civil no less than of religious society depends on the inviolability of the marriage contract. The argument of the Encyclical runs as follows: The mission of Christ was to restore man in the supernatural order. That should benefit man also in the natural order; first, the individual; and then, as a consequence, human society. Having laid down this principle, the Encyclical deals with Christian marriage which sanctifies the family, i.e. the unit of society. The marriage contract, Divinely instituted, had from the beginning two properties: unity and indissolubility. Through human weakness and willfulness it was corrupted in the course of time; polygamy destroyed its unity, and divorce its indissolubility. Christ restored the original idea of human marriage, and to sanctify more thoroughly this institution He raised the marriage contract to the dignity of a sacrament. Mutual rights and duties were secured to husband and wife; mutual rights and duties between parents and children were also asserted: to the former, authority to govern and the duty of training; to the latter, the right to parental care and the duty of reverence. Christ instituted His Church to continue His mission to men. The Church, true to her commission, has always asserted the unity and indissolubility of marriage, the relative rights and duties of husband, wife, and children; she has also maintained that, the natural contract in marriage having been raised to the dignity of a sacrament, these two are henceforth one and the same thing so that there cannot be a marriage contract amongst Christians which is not a sacrament. Hence, while admitting the right of civil authority to regulate the civil concerns and consequences of marriage, the Church has always claimed exclusive authority over the marriage contract and its essentials, since it is a sacrament. The Encyclical shows by the light of history that for centuries the Church exercised, and the civil power admitted, that authority. But human weakness and willfulness began to throw off the bridle of Christian discipline in family life; civil rulers began to disown the authority of the Church over the marriage tie; and rationalism sought to sustain them by establishing the principle that the marriage contract is not a sacrament at all, or at least that the natural contract and the sacrament are separable and distinct things. Hence arose the idea of the dissolubility of marriage and divorce, superseding the unity and indissolubility of the marriage bond. The Encyclical points to the consequences of that departure in the breaking up of family life, and its evil effects on society at large. It points out as a consequence, that the Church, in asserting its authority over the marriage contract, has shown itself not the enemy but the best friend of the civil power and the guardian of civil society. In conclusion, the Encyclical commissions all bishops to oppose civil marriage, and it warns the faithful against the dangers of mixed marriages.