During revolution we see several sentiments developed which are commonly repressed, but to which the destruction of social constraints gives a free vent. These constraints, consisting of the law, morality, and tradition, are not always completely broken. Some survive the upheaval and serve to some extent to damp the explosion of dangerous sentiments. The most powerful of these restraints is the soul of the race. This determines a manner of seeing, feeling, and willing common to the majority of the individuals of the same people; it constitutes a hereditary custom, and nothing is more powerful than the ties of custom. This racial influence limits the variations of a people and determines its destiny within certain limits in spite of all superficial changes. For example, to take only the instances of history, it would seem that the mentality of France must have varied enormously during a single century. In a few years it passed from the Revolution to Caesarism, returned to the monarchy, effected another Revolution, and then summoned a new Caesar. In reality only the outsides of things had changed. We cannot insist further here on the limits of national variability, but must now consider the influence of certain affective elements, whose development during revolution contributes to modify individual or collective personalities. In particular I will mention hatred, fear, ambition, jealousy or envy, vanity, and enthusiasm. We observe their influence during several of the upheavals of history, notably during the course of the French Revolution, which will furnish us with most of our examples. Hatred.--The hatred of persons, institutions, and things which animated the men of the Revolution is one of these affective phenomena which are the more striking the more one studies their psychology. They detested, not only their enemies, but the members of their own party. ``If one were to accept unreservedly,'' said a recent writer, ``the judgments which they expressed of one another, we should have to conclude that they were all traitors and boasters, all incapable and corrupt, all assassins or tyrants.'' We know with what hatred, scarcely appeased by the death of their enemies, men persecuted the Girondists, Dantonists, Hebertists, Robespierrists, &c. One of the chief causes of this feeling resided in the fact that these furious sectaries, being apostles in possession of the absolute verity, were unable, like all believers, to tolerate the sight of infidels. A mystic or sentimental certitude is always accompanied by the need of forcing itself on others, is never convinced, and does not shrink from wholesale slaughter when it has the power to commit it.