In 1968, Pope Paul VI promulgated his encyclical Humanae Vitae, explaining Catholic teaching on the regulation of birth. In his encyclical, Pope Paul lauds “responsible parenthood” and endorses the regulation of births when serious reasons exist for doing so (10). The decision could arise from “the physical or psychological conditions of husband or wife, or from external circumstances” (16). Pope Paul insists, however, that the methods of regulation be in harmony with the “natural laws and rhythms of fertility” created by God (11). These methods “avail themselves” of natural rhythms, while contraceptives “impede” them (16). Methods must also respect the “supernatural” end of marriage (7), marriage being a divine sacrament by which men and women grow in wisdom and holiness. Employing the healthy discipline of natural methods, spouses will “enjoy a serene and harmonious development of their spiritual and emotional faculties”, and will find themselves “capable of a deeper and more efficacious influence” on their children. Pope Paul warns that contraceptives will lead to “conjugal infidelity and to a general lowering of morality,” noting that “one does not need much experience to know human weakness and to understand that human beings—especially the young—have need of encouragement to be faithful to the moral law, and must not be offered an easy means to evade its observance” (21). This seems to have been prophetic. The natural regulation of births does require sacrifice—as does any authentic Christian life (see Lk.9:23)—yet it is also a pathway to the peace of God which “surpasses all understanding” (Phil 4:7).