This secrecy has not always been maintained. When the Catholic Church was at the summit of its power and influence it fully realized the magnitude of sexual problems and took an active and inquiring interest in all the details of normal and abnormal sexuality. Even to the present time there are certain phenomena of the sexual life which have scarcely been accurately described except in ancient theological treatises. As the type of such treatises I will mention the great tome of Sanchez, _De Matrimonio_. Here you will find the whole sexual life of men and women analyzed in its relationships to sin. Everything is set forth, as clearly and as concisely as it can be--without morbid prudery on the one hand, or morbid sentimentality on the other--in the coldest scientific language; the right course of action is pointed out for all the cases that may occur, and we are told what is lawful, what a venial sin, what a mortal sin. Now I do not consider that sexual matters concern the theologian alone, and I deny altogether that he is competent to deal with them. In his hands, also, undoubtedly, they sometimes become prurient, as they can scarcely fail to become on the non-natural and unwholesome basis of asceticism, and as they with difficulty become in the open-air light of science. But we are bound to recognize the thoroughness with which the Catholic theologians dealt with these matters, and, from their own point of view, indeed, the entire reasonableness; we are bound to recognize the admirable spirit in which, successfully or not, they sought to approach them. We need to-day the same spirit and temper applied from a different standpoint. These things concern everyone; the study of these things concerns the physiologist, the psychologist, the moralist. We want to get into possession of the actual facts, and from the investigation of the facts we want to ascertain what is normal and what is abnormal, from the point of view of physiology and of psychology. We want to know what is naturally lawful under the various sexual chances that may befall man, not as the born child of sin, but as a naturally social animal. What is a venial sin against nature, what a mortal sin against nature? The answers are less easy to reach than the theologians' answers generally were, but we can at least put ourselves in the right attitude; we may succeed in asking that question which is sometimes even more than the half of knowledge.