Like Pope Pius XII, Paul VI spoke, in his encyclical “Humanae vitae” (n 10) of the possibility of practicing periodic continence "for serious reasons and in respect for the moral Law". It is this “respect for the moral law” that interests us here. The Catholic Marriage Manual quotes on this point, Father John A. Goodwine, of St. Joseph’s Seminary, Dunwoodie, N.Y… Assuming that, in one particular case, circumstances of a medical, eugenic, social or economic nature justify periodic continence, Father Goodwine explains that there would already be sin if mutual agreement on its use was not present. “Neither partner may insist on abstinence against the reasonable protest of the other. The reason for this is the marriage contract. By that contract each partner agrees to satisfy the reasonable and serious request of the other for marital relations; for one partner to default on this contract would be a serious violation of justice. Accordingly, the practice of periodic continence would be lawful when, and just as long as, it is mutually agreeable to the spouses (Op. cit.,p.57).” Father Goodwine continues: "The second requisite is thai’ both husband and wife must be able to** practice continence during the so-called fertile days.** The use of periodic continence demands no little self-control. When a couple attempts to restrict the use of marriage to the sterile period, there may arise occasions of serious sin. The attempt may lead to sins of self-abuse, to mutual fondling to the point of culpable pollution, and even to infidelity. These dangers are especially great in the case of men; but women are by no means exempt from them.