The criminal is, however, by no means an idiot. He is not even a merely weak-minded person. The idiot and the feeble-minded, as we know them in asylums, rarely have any criminal or dangerous instincts. Another term is frequently used to denote vicious or criminal instincts in a person who is, mentally, little if at all defective; he is said to be "morally insane."
The term "moral insanity" was originated nearly half a century ago by an Englishman, Dr. Prichard, who in his _Treatise on Insanity_ declared that insanity exists sometimes with an apparently unimpaired state of the intellectual faculties; and the conception has been developed by Krafft-Ebing, Maudsley, and many others. The term itself is an unfortunate one; the condition described by no means falls in easily as a subdivision of insanity, and it is moreover frequently of a congenital character. There is now a very general tendency to drop the expression "moral insanity," and to speak instead of "moral imbecility."
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.