the magisterium of the Church. Limited rights over the body The Pope points to some Catholic dogma. Human procreation, like all questions of life, is a part of God's loving design. Married life takes its origin from God, who "is love." Husband and wife cooperate with God in the generation and rearing of new lives. Married love must therefore be more than a question of natural instinct or emotional drive. It is faithful and exclusive until death. Parents are not free to act as they choose in the service of transmitting life, as if it were wholly up to them to decide what is the right course to follow. Observing the Natural Law means that each and every marital act must of necessity retain its intrinsic relationship to the procreation of human life. Faithfulness to God's Design means to experience married love while respecting the laws of conception and to acknowledge that one is not the master of the sources of life but rather the minister of the design established by the Creator. All artificial birth control methods are unlawful as are all specifically intended to prevent procreation—whether as an end or as a means. Lawful Therapeutic Means are permitted if necessary to cure bodily diseases, even if a foreseeable impediment to procreation should result, provided such impediment is not directly intended for any motive whatsoever. Recourse to Infertile Periods applies to the spacing of births, arising from the physical or psychological condition of the husband or wife, or from external circumstances. The Church teaches that married people may then take advantage of the natural cycle. Scientists, as already requested by Pius XII, should study natural rhythms as a secure basis for the limitation of offspring. Control of the body Pope Paul fully realizes that Humanae vitae is not easy to follow. Some may argue that it teaches the impossible. He discusses the value of self-discipline of the body and self-denial of bodily pleasures as a source of family tranquility, peace, and personality development within the family. He recommends chastity within marriage and appeals to public authorities not to tolerate any legislation that would introduce into the family practices that are opposed to the natural law of God. Social and economic development The Pope is fully aware of the developmental implications of this teaching. Regarding worldwide development he quotes Pope John XXIII that no solution is acceptable which violates man's