This illustration relates to the elucidation of the causes of a tumult which occurred in Esthonia in the year 1905. The judge before whom the persons arrested during the suppression of the revolt have been brought wishes to discover who were the ringleaders; the psychologist wishes to ascertain to what extent imitation, suggestion, or hypnotic automatism, has impelled certain ordinarily law-abiding citizens to take part in the disturbances; the editor of the local Marxian newspaper demonstrates the causes of the revolt by an analysis of capitalism in general, and of the economic and social characteristics of the government of the disturbed section; the reactionary politician will consider that the fault lies in irreligion, in the disturbing effect of revolutionary agitation, and in the decline in the authority of a government in which constitutionalism has replaced absolutism, and whose punitive measures have lost their former repressive severity. But if Lombroso had been summoned to the prisons of Liebau, Riga, Dorpat, and Reval, and had been invited to ascertain the causes of the Letto-Esthonian jacquerie, he would have examined the meteorological records at the time of the disturbances; would have inquired carefully regarding the racial origin of the persons arrested; would have looked for stigmata of degeneration in their physiognomy and physical characteristics, especially those of the skull; would have noted how many epileptics, hysterics, lunatics, and alcoholics there were among them; would have distinguished the habitual vagrants and those with previous convictions. Among the women arrested during the jacquerie, he would have asked how many were menstruating at the time; he would have made a list of the adolescents entirely dominated by fanatical doctrines; a list of the agents provocateurs; a list of those instigated by feelings of personal animosity against the local landed gentry and their retainers. And when all this had been done, it is very doubtful if among the accused there would then remain any considerable residuum in whom an advocate of the materialist conception of history would be able to prove the existence of a purely economic determination to the offences with which they have been charged. And even if Lombroso, as is not improbable, should have found among those arrested or liable to arrest some disciples of Bebel or of Schönlank, his analysis of their inherited tendencies, their gynæcological state, their sensibility and reflexes, the shape of their skulls and the extent of their visual fields, would ultimately bring to light determinants of their actions quite other than their acquired orthodox Marxism, which a jurist of the school of Plehve would have denounced as the _vera causa_, or sufficient reason, for their participation in the disturbance.