By Roman Catholics it is held to be a mortal sin to employ any chemical or mechanical means to prevent conception, the only permissible form of control being voluntary abstinence from each other on the part of both parents. The abstinence of one parent against the will of the other is also considered a mortal sin on the part of the refractory parent. An exception to this rule is now made which permits parents not desiring children to make use of a moment in the periodic life of the mother during which conception is less likely to take place than at other times――the so-called ‘safe’ period. It is, however, generally agreed nowadays that the ‘safety’ pertaining to this period is in many cases quite illusory and devoid of serious physiological or medical basis. Opponents of the Roman Catholic Church have represented its insistence on this prohibition as dictated by a desire to extend her spiritual empire throughout the world, since obedience to it must bring about a greater relative increase of believing Roman Catholics than of adherents to other religious denominations tolerating Birth Control. But its attitude would further appear to express a conviction (manifested elsewhere in the insistence upon celibacy among Catholic priests and in its systems of penances and abstinences) that sexual indulgence is somehow incompatible with devotion to a purely spiritual life, and when excessive produces a demoralizing effect upon human nature, tending to make it weak, lazy, selfish and often vicious. Probably the Catholic Church feels that the use of devices to prevent conception would abolish the necessity for salutary self-restraint, and would promote promiscuous and excessive indulgence. The effect of this prohibition is that most Catholics who are conscientious about not using contraceptives have large families. There are some, however, particularly in France, who do not take the prohibition very seriously. At the bottom, however, of the religious objection, would appear to lie the conviction that excessive sexual indulgence, dissociated from the sequel of procreation and rendered possible by the use of contraceptives, is morally harmful to the individual. 8. An objection of a pseudo-political nature is sometimes heard which envisages a bureaucratic extension of Birth Control. The phrase is here understood to imply a ‘National Control of Births’ and not a ‘Voluntary Regulation of Births’, its more usual acceptance. Such a bureaucratic interference in people’s private lives is held to constitute an infringement of the liberty of the individual――in this case his liberty to have as many children as he likes, when he likes. The principle of individual liberty, the corner-stone of nineteenth century Liberalism, still has a certain number of adherents.