"When the Christian religion is reflected and repudiated, marriage sinks of necessity into the slavery of man's vicious nature and vile passions, and finds but little protection in the help of natural goodness. A very torrent of evil has flowed from this source, not only into private families, but also into States. For, the salutary fear of God being removed, and there being no longer that refreshment in toil which is nowhere more abounding than in the Christian religion, it very often happens, as indeed is natural, that the mutual services and duties of marriage seem almost unbearable; and thus very many yearn for the loosening of the tie which they believe to be woven by human law and of their own will, whenever incompatibility of temper, or quarrels, or the violation of the marriage vow, or mutual consent, or other reasons induce them to think that it would be well to be set free."
(Pope Leo XIII, Arcanum, On Christian Marriage, 1880)
"If, then, we consider the end of the divine institution of marriage, we shall see very clearly that God intended it to be a most fruitful source of individual benefit and of public welfare, Not only, in strict truth, was marriage instituted for the propagation of the human race, but also that the lives of husbands and wives might be made better and happier. This comes about in many ways: by their lightening each other's burdens through mutual help; by constant and faithful love; by having all their possessions in common; and by the heavenly grace which flows from the sacrament. Marriage also can do much for the good of families, for, so long as it is conformable to nature and in accordance with the counsels of God, it has power to strengthen union of heart in the parents; to secure the holy education of children; to temper the authority of the father by the example of the divine authority; to render children obedient to their parents. . ." (Pope Leo XIII, Arcanum, 1880)