Observing the Natural Law
11. The sexual activity, in which husband and wife are intimately and chastely united with one another, through which human life is transmitted, is, as the recent Council recalled, “noble and worthy” (cf. Gaudium et Spes, n. 49). It does not, moreover, cease to be legitimate even when, for reasons independent of their will, it is foreseen to be infertile. For its natural adaptation to the expression and strengthening of the union of husband and wife is not thereby suppressed. The fact is, as experience shows, that new life is not the result of each and every act of sexual intercourse. God has wisely ordered laws of nature and the incidence of fertility in such a way that successive births are already naturally spaced through the inherent operation of these laws. The Church, nevertheless, in urging men to the observance of the precepts of the natural law, which it interprets by its constant doctrine, teaches that each and every marital act must of necessity retain its intrinsic relationship to the procreation of human life (cf. Pius XI, Casti connubi).
Natural Law, remember, is that which we naturally know as right vs. wrong because God placed that knowledge within us along with a conscience which tells us to do good and avoid evil. Sex is a gift given by God to a husband and wife for the twin purposes of strengthening the bond between them (as they are no longer two but one flesh) and bringing children into the world. Even if a couple is unable to have children, the conjugal act is still “noble and worthy” assuming that they are at least open to having children.
That last line is of great importance: “each and every marital act must of necessity retain its intrinsic relationship to the procreation of human life.” Contraception willingly severs that intrinsic relationship between the marital act and the procreation of life. And that is why the use of artificial contraception is always by its very nature a mortal sin. Mortal sins cut us off from God’s grace which gives life to our souls (whereas venial sins wound that connection). The use of contraception is a mortal sin because it destroys God’s plan for man and woman to “be fruitful and multiply”.
See references in the Catechism of the Catholic Church:
nn. 1854-1864 on “The Gravity Of Sin: Mortal And Venial Sin”
(Posted with permission from Fr. Lee Acervo at http://fatheracervo.wordpress.com)
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