Quantitatively considered, the greater part of Lombroso’s life-work has been devoted to the study of social phenomena bearing upon the fact that every society contains certain categories of pathological or abnormal individuals, whose behaviour has a disturbing influence upon the regular social life. But however interesting and important in relation to the practical working of State and society may be the social interconnections thus brought to light, it is certainly not possible from the knowledge of these alone to deduce a system of sociology; for example, we do not obtain an adequate knowledge of the remarkable social phenomenon of prostitution simply by means of the biological study of the anomalies of a large number of individual prostitutes, and by the proof that these anomalies are analogous to those whose presence may be demonstrated in criminal types. For, although this explains the sociological fact of the existence of a supply of purchaseable sexual pleasure, it does not explain the existence of the demand for the same commodity. Lombroso was gradually induced, not only by the critical powers with which he was so richly endowed (and which led him repeatedly to the view that most of the phenomena he was investigating were produced by purely social factors), but, in addition, by the general tendency of his mind, to show, not merely that the existence of numerous abnormalities and degenerative varieties of mankind disturbs the life of society, but, further, that the political and economic development of the civilized nations gives rise to the appearance of abnormalities which themselves induce social reactions—and to demonstrate that these cannot be got rid of by reformatory measures, will not disappear with the removal of the cause, but lead to permanent biological individual variations, and, through inheritance, produce anomalies for generations to come, and in this way give rise to long-enduring social injury or disturbance. In the first place it is to him that we owe the knowledge that a given social and economic order can give rise to transmissible biological anomalies, and that those who suffer from these anomalies, ill-adapted for any social and economic order, necessarily exercise a disturbing influence in society. It was not merely as a positivist that he was led to this view, but, above all, as an anthropologist. This knowledge is the most important contribution which Lombroso’s life-work has given to sociology. But it does not stand alone.