In Chesterton’s day, the leading criminologists believed that criminal behavior was a form of illness. Consequently, they attempted a program of “rehabilitation” of criminals that was analogous to medical treatment. The causes of crime were thought to derive exclusively from heredity and environment.

Chesterton’s line of attack was to insist on free will and the role of human responsibility in the choices made both by criminals and by the law abiding. Chesterton is all common sense on this subject:

A man may lie still and be cured of a malady. But he must not lie still if he wants to be cured of a sin. If a man is to be saved from influenza, he may be a patient. But if he is to be saved from forging, he must be not a patient but an impatient. He must be personally impatient with forgery. All moral reform must start in the active not the passive will.

Imprisonment, Chesterton believed, must be thought of as a specific punishment for a specific crime. If imprisonment were thought of as therapeutic, he reasoned, convicts would be kept in jail until some “expert” decided they had “recovered” (had been rehabilitated). If heredity and environment account for all crimes, he argued, then law enforcement would become focused on certain types of people (perhaps the poor) and in certain neighborhoods (perhaps the slums).

According to Philip Jenkins, an expert on both Chesterton and on criminology, Chesterton’s ideas were considered bizarre by the experts of his own day, but have now become accepted as “mainstream” by the criminology establishment and the courts. Jenkins calls Chesterton the “forgotten prophet” in this field.