Deliberate interference with marital intercourse in order to prevent conception. It is the performance of the marriage act with the positive frustration of conception. Also called conjugal onanism, from the sin of Onan, referred to in the Bible (Genesis 38:8-10); Neo-Malthusianism from the name of the English sociologist Malthus (1766-1834); it is popularly termed birth control, where those concerned with high birthrates have come to equate contraception with population control.
The Catholic Church has forbidden contraception from earliest times, and the number of papal statements dealing with the subject indicates the Church's constant tradition. In modern times the most significant document was Humanae Vitae in 1968 by Paul VI. After referring to the long history of the Church's teaching, he declared that the "direct interruption of the generative process already begun," even though done for therapeutic reasons, is to be "absolutely excluded as a licit means of regulating birth." Equally to be excluded is direct sterilization for contraceptive reasons. "Similarly excluded is every action that, either in anticipation of the conjugal act, or in its accomplishment, or in the development of its natural consequences, purposes, whether as an end or as a means, to render procreation impossible" (Humanae Vitae, II, 14).
Few aspects of Christian morality in modern times have given rise to more difficulties of conscience than the Catholic doctrine on contraception. This was reflected in Paul's admission, shortly after Humanae Vitae: "How many times we have trembled before the alternatives of an easy condescension to current opinions."
One of the results of the Church's teaching on contraception has been to emphasize her right to teach the faithful, even to binding them gravely in conscience, in matters that pertain to the natural law. Yet the basic motivation offered to married people to live up to this difficult teaching is highly supernatural, namely the prospect of loving one another in such a way that they will share the fruits of their affection with another person whom their mutual love will bring into being.