27 These many and glorious fruits were ever the product of marriage, so long as it retained those gifts of holiness, unity, and indissolubility from which proceeded all its fertile and saving power; nor can anyone doubt but that it would always have brought forth such fruits, at all times and in all places, had it been under the power and guardianship of the Church, the trustworthy preserver and protector of these gifts. But, now, there is a spreading wish to supplant natural and divine law by human law; and hence has begun a gradual extinction of that most excellent ideal of marriage which nature herself had impressed on the soul of man, and sealed, as it were, with her own seal; nay, more, even in Christian marriages this power, productive of so great good, has been weakened by the sinfulness of man. Of what advantage is it if a state can institute nuptials estranged from the Christian religion, which is the mother of all good, cherishing all sublime virtues, quickening and urging us to everything that is the glory of a lofty and generous soul? 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. Then, if they are hindered by law from carrying out this shameless desire, they contend that the laws are iniquitous, inhuman, and at variance with the rights of free citizens; adding that every effort should be made to repeal such enactments, and to introduce a more humane code sanctioning divorce.
Source: Arcanum Divinae (Vatican.va)