351. The sixth commandment of the Church is, "Not to marry that are not Catholics, or that are related to us within the fourth degree of kindred; nor privately without witnesses, nor to solemnize marriage between the first Sunday of Advent and the Epiphany, nor between Ash Wednesday and Low Sunday". The laws which the Church has made on the subject are full of wisdom; they rest both on the Word of God and on the nature of man, and their usefulness has been tested by the experience of ages. Those who seek dispensations from them are likely to incur, for themselves and their children, the evil consequences which these laws are intended to prevent. The great importance of marriage requires that it be hedged in with strong safeguards, to prevent private and public harm. Therefore the Church has established certain hindrances, called impediments to the marriage bond; some of these, styled "diriment", make the contract affected by them invalid, or null, while others are "merely prohibitive".
The diriment impediments regard chiefly: 1. Substantial error as to the identity of the parties. 2. Violence, or compulsion. 3. Relationship, by blood or affinity, extending to the fourth degree of kindred inclusively. 4. Solemn vows. 5. Disparity of worship, which exists when one of the parties is not baptized. 6. Certain crimes affecting married persons, 7. Clandestinity, or the non-observance of the legal formalities which require the presence of the parish priest of either party and the presence of two witnesses. This law, called "Tametsi", was enacted by the Council of Trent to protect both the Sacrament and the persons contracting. It was to have no invalidating effect in any parish till after promulgation in the same; and, as a consequence, it has not yet any such effect wherever it has never been promulgated, for instance in almost all parts of the United States. Still clandestine marriages are forbidden under sin whenever they can be avoided. (See for a fuller explanation of these impediments "Messenger Magazine" for May, 1903, pp. 532 etc).
Among the merely prohibitive impediments the most important is that which forbids mixed marriages, that is marriages of Catholics with non-Catholics, even though the latter be baptized. This prohibition dates back at least to the Council of Chalcedon, A. D. 451 (Acts 15, can. 14), and it has often been renewed by Councils and Sovereign Pontiffs. Such marriages are apt to interfere considerably with the chief purposes of Christian Matrimony, especially with its permanency, with union of minds among the parents, and with the proper education of the children. Marriage should be an aid, not a hindrance in the way of salvation; now such unions, as experience shows, are likely to ruin the faith of the Catholic party, or at least greatly to hinder its practice, and to make the proper education of the children almost impossible (See "Messenger Magazine" for Oct. 1902).
The Church cannot grant dispensations from the laws which God has enacted; thus she has never claimed the power of dissolving a consummated Christian marriage. Nor can she dispense when the rights of individuals are involved. But she can grant exemptions in her own laws; still she never does so except when more harm than good would result from the refusal of the dispensation. How faithfully her ministers have guarded the sanctity of the marriage bond, is seen by their unyielding opposition to such tyrants as Henry VIII. of England, the first Napoleon, etc. As long as the marriage has not been consummated, she can allow either partner to withdraw from it for very weighty reasons, for instance to enter upon the more sacred contract of solemn religious vows.
St. Paul has established a special exemption, called "the Pauline privilege", which allows one converted to Christianity to leave a non-baptized husband or wife, and to marry a Christian instead, if peaceful co-habitation with the former partner become impossible: "If the unbeliever depart, let him depart; for a brother or sister is not under servitude in such a case. But God has called us in peace. (1 Cor. VII, 15).
Before granting to any of her children a dispensation to marry a non-Catholic, the Church requires, as an indispensible condition, a solemn promise that the Catholic party shall have the free exercise of religion, and shall endeavor to lead the other party by conviction to the true faith; also that all the children to issue from this marriage shall be educated as Catholics. To secure all needed safeguards of so important a Sacrament, Holy Church requires that the bans of matrimony be duly proclaimed in the parish churches of both parties; so that, if any impediment to the intended contract should exist, it may he discovered in good time. This observance is most honorable to the parties concerned; for no suspicion of reproach can rest upon an alliance which has stood this public test of its integrity. St. Liguori, the most recent writer that is honored as a Doctor of the Church, in his popular "Instructions on the Commandments and Sacraments", has these practical suggestions: "Matrimony is free; but let children remember that they can rarely be excused from mortal sin if they contract marriage against the will of their father and mother".
In a matter as important as it is delicate, the holy Doctor draws his teachings directly from the Word of God; for he says: "Let us observe in the example of the son of the Patriarch Tobias (Tob. VI) the manner in which young persons should contract marriage. In the city of Rages, in Media, there was a holy girl, called Sara, the daughter of Raguel, who was greatly afflicted because seven young men, on the nights of their nuptials with her, were, one after the other, strangled by the devil Asmodeus. The son of Tobias was afterwards destined to be the spouse of Sara. Having heard of the unhappy death of her former husbands, he was afraid to contract marriage with her. But, to remove his fear, the Angel Raphael, who accompanied him, said 'Know that the persons over whom the devil has power, are those who engage in matrimony, not to please God, but for sensual gratification. Do not imitate such persons; take Sara for your wife, not to indulge concupiscence, but rather to bring up children who shall serve and bless God; and thus you shall have nothing to fear from the devil'. Thus the holy youth acted, and benedictions were poured abundantly on his marriage".
St. Alphonsus concludes his "Instructions" with the following four admonitions, which her parents gave to Sara when she took leave of them (Tob. X, 13): "First, said they, show respect to your father-in-law and mother-in-law. Secondly, love your husband. Thirdly, attend to the government of the family. Fourthly, conduct yourself in such a manner that none of your actions may deserve censure" (pp. 254, 255).