Marriages sometimes break up because people have an unclear idea of what marriage is, why it exists, and why it requires such commitment. Many marry based on feelings, with little thought to the nature of the institution. The procreative purpose of marriage, which by natural law is its primary end, is especially neglected. Some married couples plan from the outset never to have children, denying an essential property of marriage (openness to fertility) that is required for it to be validly contracted.
Catholic theology has always recognized that, according to natural law and the Bible, marriage is not only for the companionship and mutual love of the spouses but also for the procreation of children.
Thomas Aquinas stated, “It is clear that offspring is the most essential thing in marriage, secondly fidelity, and thirdly [the] sacrament; even as to man it is more essential to be in nature than to be in grace, although it is more excellent to be in grace” (Summa Theologiae IIIb:49:3).
The Catechism of the Catholic Church says, “By its very nature the institution of marriage and married love is ordered to the procreation and education of the offspring, and it is in them that it finds its crowning glory” (CCC 1652). “Married couples should regard it as their proper mission to transmit human life and to educate their children” (CCC 2367).
The following passages show the Fathers clearly understood this natural law purpose of marriage, though they also recognized that other benefits (such as companionship, mutual love, physical pleasure, and the release of sexual tension) also follow from it.
But whether we [Christians] marry, it is only that we may bring up children; or whether we decline marriage, we live continently (1st Apology 29 [A.D. 151]).
Therefore, having the hope of eternal life, we despise the things of this life, even to the pleasures of the soul, each of us reckoning his wife whom he has married according to the laws laid down by us, and that only for the purpose of having children” (Plea for the Christians33 [A.D. 177]).
Clement of Alexandria
Since pleasure and desire seem to fall under marriage, it must also be treated of. Marriage is the first conjunction of man and woman for the procreation of legitimate children. . . . Neither ought everyone take a wife, nor every woman take [a husband], nor always, nor in every way, nor inconsiderately. But [she is to take] he who is in certain circumstances, and such a one as and at such time as is requisite, and for the sake of children, and one who is in every respect similar [to her], and who does not by force or compulsion love the husband who loves her. . . . Now marriage is [also] a help in the case of those advanced in years, by furnishing a spouse to take care of one, and by rearing children of her to nourish one’s old age” (Stromata 2:23 [A.D. 206]).
Clement of Alexandria
When the apostle [Paul] says it is good not to touch a woman [1 Cor. 7:1], he speaks not to those who chastely use marriage for procreation alone, but to those who were desiring to go beyond procreation, lest the adversary raise a strong blast and arouse desire for foreign pleasures [ie. adultery] (ibid. 3:15:96).
We [Christians] do not indeed forbid the union of man and woman, blessed by God as the generator of the human race, and devised fro the replenishment of the earth and the furnishing of the world, and therefore permitted, yet singly [monogamously] (To My Wife 2 [A.D. 207]).
By choice we [Christians] are bound by the bond of a single marriage with the desire of procreating (Octaius 31:5 [A.D. 226]).
But in the New Covenant also there are some legal injunctions [given in concession to human weakness], for example, because of our hardness of heart, it has been written on account of our weakness, “But because of fornications, let each man have his own wife and let each woman have her own husband” [1 Cor. 7:2] (Commentary on Matthew 14:23 [A.D. 248]).
Whoever cannot control his affections, let him keep them within the limits of a lawful bed (Divine Institutes 6:23:3 [A.D. 307]).
God gave us eyes not to see and desire pleasure, but to see acts to be performed for the needs of life; so too, the genital [‘generating’] part of the body, as the name itself teaches, has been received by us for no other purpose than the generation of offspring (ibid. 6:23:18).
Cyril of Jerusalem
Let those . . . be of good cheer who are married and use their marriage properly; who enter marriage lawfully and not out of wanton and unbounded license; who recognize periods of continence so that they may give themselves to prayer; who in the assemblies bring clean bodies as well as clean garments into church; who have embarked upon the matrimonial estate for the procreation of children, and not for the sake of indulgence (Catechetical Lectures 4:25 [A.D. 350]).
Cyril of Jerusalem
And those who are once married-let them not hold in contempt those who have accommodated themselves to a second marriage. Continence is a good and wonderful thing; but still, it is permissible to enter upon a second marriage, lest the weak might fall into fornication (ibid. 4:26 [A.D. 350]).
There are two reasons why marriage was instituted, that we may live chastely and that we may become parents (On Those Words of the Apostle “On Account of Fornication”‘ [A.D. 392]).
There is no great reason to have money while there is great reason to have wives to preserve chastity; hence no one blames a man who has lawful intercourse with his wife into old age, but all blame him who accumulates money (Homilies on Titus 5 [A.D. 395]).
[A wife is] espoused to her husband to be his partner in life, and for the procreation of children, not for the purposes of indecency and laughter; that she might keep the house, and instruct him also to be serious, not that she might supply to him the fuel of fornication [Homilies on 1 Thessalonians 5 [A.D. 400]).
Among all nations and all men, therefore, the advantage of marriage is for the sake of begetting offspring and in the fidelity of chastity. In the case of the people of God, however, there is also the holiness of the sacrament, on which account a woman is not permitted, even when she leaves with a repudiation, to marry another while her husband yet lives, not even for the sake of bearing children. Although this is the only reason why marriage takes place, even if this for which marriage takes place does not follow, the marriage bond is loosed only by the death of a spouse (On the Good of Marriage 24:32 [A.D. 401]).
In marriage, however, let the blessings of marriage be loved: offspring, fidelity, and the sacramental bond. Offspring, not so much that it may be born, but because it can be reborn [as a Christian]; for it is born to punishment unless it be reborn to life. Fidelity, but not such as even the unbelievers have among themselves, ardent as they are for the flesh. . . . The sacramental bond, which they lose neither through separation nor through adultery-this the spouses should guard chastely and harmoniously (Marriage and Concupiscence 1:17:19[A.D. 419]).
The procreation of children is the first and natural and lawful reason for marriage (On Adulterous Marriages 2:12:12 [A.D. 419]).