Different writers have made their catalogues of causes that are responsible for crime, and most of these lists are more or less correct. There can be no doubt that more crimes against property are committed in cold weather than in warm weather; more in hard times than in good times; more by the unemployed than the employed; more during strikes and lockouts than in times of industrial peace; more when food is expensive and scarce than when it is cheap and plenty; more, in short, when it is harder to live. There is no doubt that there are more crimes of violence in extreme hot weather than in cold weather. That is, heat affects crimes as it affects disease and insanity and death; in short, as it affects all life. More crimes of violence are committed after wars or during heated political campaigns than at other times; more of such crimes when, either by climatic or other conditions, feelings are intensified or aroused and less subject to control. Likewise there are more crimes committed by young men between seventeen and twenty four or five years of age than at any other age. Neither the very young nor the old commit crimes, except in rare cases. All the old people could be safely dismissed from prisons. Some few of the senile would need attention, and many need support and care, but none is dangerous to the community. There can be no question that practically all criminals are poor. Even when bankers get into prison they almost never have much money when they start that way, and none when they arrive. They are sent for something that would not have happened except for financial disaster. There is no longer any question that a large number, say probably from ten to twenty per cent of the convicted are, in fact, insane at the time the act was committed, and that the demented, the imbecile, and the clearly subnormal constitute many more than half of the inmates of prisons. Most of the rest can be accounted for by defective nervous systems, excessively strong instincts in some directions, weak ones in another, or a very hard environment. Add to this the facts that only a few have ever had any education worthy of the name, that most of them have never been trained to make a fair living by any trade or occupation, that almost all have had a poor early environment with no chance from the first, and most of them have had a very imperfect heredity. In short, sufficient statistics have been gathered and enough is known to warrant the belief that every case of crime could be accounted for on purely scientific grounds if all the facts bearing on the case were known.