That synthesis which mighty geniuses have often succeeded in creating by one inspiration (but at the risk of errors, for a genius is only human and in many cases more fallacious than his fellow-men) was deduced by me gradually from various sources--the study of the normal individual, the lunatic, the criminal, the savage, and finally the child. Thus, by reducing the penal problem to its simplest expression, its solution was rendered easier, just as the study of embryology has in a great measure solved the apparently strange and mysterious riddle of teratology. But these attempts would have been sterile, had not a solid phalanx of jurists, Russian, German, Hungarian, Italian, and American, fertilised the germ by correcting hasty and one-sided conclusions, suggesting opportune reforms and applications, and, most important of all, applying my ideas on the offender to his individual and social prophylaxis and cure. Enrico Ferri was the first to perceive that the congenital epileptoid criminal did not form a single species, and that if this class was irretrievably doomed to perdition, crime in others was only a brief spell of insanity, determined by circumstances, passion, or illness. He established new types--the occasional criminal and the criminal by passion,--and transformed the basis of the penal code by asking if it were more just to make laws obey facts instead of altering facts to suit the laws, solely in order to avoid troubling the placidity of those who refused to consider this new element in the scientific field. Therefore, putting aside those abstract formulæ for which high talents have panted in vain, like the thirsty traveller at the sight of the desert mirage, the advocates of the Modern School came to the conclusion that sentences should show a decrease in infamy and ferocity proportionate to the increase in length and social safety. In lieu of infamy they substituted a longer period of segregation, and for cases in which alienists were unable to decide between criminality and insanity, they advocated an intermediate institution, in which merciful treatment and social security were alike considered. They also emphasised the importance of certain measures which hitherto had been universally regarded as a pure abstraction or an unattainable desideratum--measures for the prevention of crime by tracing it to its source, divorce laws to diminish adultery, legislation of an anti-alcoholistic tendency to prevent crimes of violence, associations for destitute children, and co-operative associations to check the tendency to theft. Above all, they insisted on those regulations--unfortunately fallen into disuse--which indemnify the victim at the expense of the aggressor, in order that society, having suffered once for the crime, should not be obliged to suffer pecuniarily for the detention of the offender, solely in homage to a theoretical principle that no one believes in, according to which prison