When we examine the course of crime in France during the period 1826–80, we see a considerable increase in the crimes against property, morals, and persons, while the economic conditions have improved during these years even for the proletariat. To what cause is this increase to be ascribed? It is impossible to attribute it to a relaxation of the strictness of the police and the courts, for the activity of these has become greater. Further, where it is evident that there are such strong causes of crime, it would be madness to think that a greater severity of penalties leads to a diminution of criminality. It is for this reason that the school to which the author belongs insists not upon the increase of penalties, but rather upon the elimination of causes. Hence the doctrine of “penal substitutes.” The true cause is the following: The more abundantly a man is nourished, the more his organic forces are developed; there is, therefore, a greater activity which may express itself in more acts of honest labor, but may also express itself in an increased number of unlawful acts. And then we must not lose sight, especially with regard to sexual crimes, of the existence of a biological and of a sociological law, namely, first, that the generative force of animals and of man increases in proportion to the abundance and ease of nutrition; second, that by a continual development of foresight, the nations which follow the advice of Malthus are more and more giving the lie to the law that he formulated, since with them population shows a tendency to increase less rapidly than the means of existence, and almost in inverse proportion to wealth. This is why criminality is increasing in France, where the system of foresight is greatly developed, and where the population enjoys better nutrition than formerly. Professor Ferri is of the opinion that we can derive from the observed facts the following rules: first, criminality increases in extent but diminishes in violence; second, scarcity makes crimes against property increase, and decreases those against persons, while abundance has the opposite effect; third, civilization decreases the number of homicides, but increases that of suicides; fourth, a development of foresight with regard to births prevents an excessive increase of the population, and consequently an excessive increase of pauperism, but increases the figures for sexual crimes.