Faithfulness to God's Design

13. It is in fact justly observed that a conjugal act imposed upon one's partner without regard for his or her condition and lawful desires is not a true act of love, and therefore denies an exigency of right moral order in the relationships between husband and wife. Hence, one who reflects well must also recognize that a reciprocal act of love, which jeopardizes the responsibility to transmit life which God the Creator, according to particular laws, inserted therein, is in contradiction with the design constitutive of marriage, and with the will of the Author of life. To use this divine gift destroying, even if only partially, its meaning and its purpose is to contradict the nature both of man and of woman and of their most intimate relationship, and therefore it is to contradict also the plan of God and His will. On the other hand, to make use of the gift of conjugal love while respecting the laws of the generative process means to acknowledge oneself not to be the arbiter of the sources of human life, but rather the minister of the design established by the Creator. In fact, just as man does not have unlimited dominion over his body in general, so also, with particular reason, he has no such dominion over his generative faculties as such, because of their intrinsic ordination towards raising up life, of which God is the principle. "Human life is sacred," Pope John XXIII recalled; "from its very inception it reveals the creating hand of God." (13) 

Illicit Ways of Regulating Birth

14. In conformity with these landmarks in the human and Christian vision of marriage, we must once again declare that the direct interruption of the generative process already begun, and, above all, directly willed and procured abortion, even if for therapeutic reasons, are to be absolutely excluded as licit means of regulating birth. (14)

Equally to be excluded, as the teaching authority of the Church has frequently declared, is direct sterilization, whether perpetual or temporary, whether of the man or of the woman. (15) Similarly excluded is every action which, either in anticipation of the conjugal act, or in its accomplishment, or in the development of its natural consequences, proposes, whether as an end or as a means, to render procreation impossible.(16).

To justify conjugal acts made intentionally infecund, one cannot invoke as valid reasons the lesser evil, or the fact that such acts would constitute a whole together with the fecund acts already performed or to follow later, and hence would share in one and the same moral goodness. In truth,