The condition in question, by whatever name it is called, is described by alienists as an incapacity to feel, or to act in accordance with, the moral conditions of social life. Such persons, it has been said, are morally blind; the psychic retina has become anæsthetic. The egoistic impulses have become supreme; the moral imbecile is indifferent to the misfortunes of others, and to the opinions of others; with cold logic he calmly goes on his way, satisfying his personal interests and treading under foot the rights of others. If he comes in contact with the law then his indifference changes into hate, revenge, ferocity, and he is persuaded that he is in the right. Although so defective on the moral side, these persons are well able to make use of the abstracted intellectual conceptions of honour, morality, philanthropy; such words are indeed frequently on their lips, and it is quite impossible to convince them of the unusual character of their acts. They are absolutely and congenitally incapable of social education, systematically hostile to every moralising influence. Being themselves morally blind, it is their firm conviction that all others are in the same condition; they disbelieve in the possibility of virtue, and being often possessed of considerable intellectual ability, maintain anti-social theories with much skill. “Moral insanity” does not probably stand for any definite morbid condition. It is used as a convenient term to describe a certain group of psychic symptoms which are not found in a developed condition in the normal man. It is obvious that these symptoms closely resemble those we have already described as characterising the criminal in his most clearly-marked form--the instinctive criminal. The morally insane person has been identified with the instinctive criminal by Lombroso, Marro, Ferri, Benedikt, Colajanni, and many others. The fusion has, however, been rejected by some--by Binswanger and Kraepelin, for instance. There can, however, be little doubt that the two groups overlap in very large part. The group of instinctive criminals therefore still stands fairly apart among the other groups of criminals, approximating, but not fusing with, these various morbid and atypical groups. The outlines blend, but each group is distinct at the centre. It will be the work of the future to arrange, and if necessary to re-form, these various groups. It is much to be able to see, even so clearly as we do to-day, the human classes of arrested or perverted development who lie in the dark pool at the foot of our social ascent. Even our present knowledge is sufficient to serve as the justification for a certain amount of social action. We owe this to the labours of a succession of physiologists, alienists, anthropologists, and criminologists during the past century.