Many of these questions can be answered only by a study of individual experiences. Vices undoubtedly have their natural history, like certain forms of disease. They may therefore be regarded as independent entities which find their habitat in human environment, are stimulated by certain conditions, inhibited by others, but invariably exhibit through all changes a character that is typical. In the early days the temperance movement had something of the character of a religious revival, and the effects were highly picturesque. In recent years the leaders have displayed a more deliberate strategy, but the struggle against the liquor traffic still has all the characteristics of a big popular movement, a movement which, having first conquered the rural districts, is now seeking to enforce itself in the cities. On the other hand, the vice crusade started with the cities, where, in fact, commercialized vice is indigenous. The mere discussion of this subject in public has meant an enormous change in the sex mores. The fact that this movement is everywhere coincident with the entrance of women into a greater freedom, into industry, the professions, and party politics, is significant. There are conditions peculiar to the life of great cities (referred to under the heading “Mobility of the Population of Great Cities”) which make the control of vice especially difficult. For example, crusades and religious movements generally do not have the same success in the city environment that they do in the smaller and less heterogeneous communities. What are the conditions which make this true? Perhaps the facts most worth studying in connection with the movement for suppression of vice are those which indicate the changes which have taken place in fifty years in sex mores, particularly with reference to what is regarded as modest and immodest in the dress and behavior, and with reference to the freedom with which sexual matters are now discussed by young men and young women. It seems, in fact, as if we were in the presence of two epoch-making changes, the one which seems destined finally to put intoxicating liquors in the category of poisonous drugs, and the other to lift the taboo which, particularly among Anglo-Saxon peoples, has effectually prevented up to the present time the frank discussion of the facts of sex.