"Among the most important of man's faculties is the sexual power. Its chief purpose is the generation of new life. This purpose pertains to the social order; it concerns the common good rather than the individual good. When husband and wife perform their marital functions in the natural manner, they are concurring in the designs of God toward the preservation and the propagation of the human race. The full import of this objective is perceived only by those who admit the eternal destiny of mankind. To them parenthood means, not merely the procreation of another member of society, but primarily coöperation with the Almighty in the creation of an immortal soul that is destined to be happy with God forever. However, when husband and wife deliberately and positively frustrate the procreative purpose of sexual intercourse, they pervert the order of nature and thus directly oppose the designs of nature's Creator. And since the reproductive function is so vital to the upkeep of the race, and since any exception to this law would be multiplied indefinitely, every act of contraceptive frustration is a gravely immoral act, or, in Catholic terminology, a mortal sin."