Up to now these thoroughgoing destructions of a worn-out civilisation have constituted the most obvious task of the masses. It is not indeed to-day merely that this can be traced. History tells us, that from the moment when the moral forces on which a civilisation rested have lost their strength, its final dissolution is brought about by those unconscious and brutal crowds known, justifiably enough, as barbarians. Civilisations as yet have only been created and directed by a small intellectual aristocracy, never by crowds. Crowds are only powerful for destruction. Their rule is always tantamount to a barbarian phase. A civilisation involves fixed rules, discipline, a passing from the instinctive to the rational state, forethought for the future, an elevated degree of culture--all of them conditions that crowds, left to themselves, have invariably shown themselves incapable of realising. In consequence of the purely destructive nature of their power crowds act like those microbes which hasten the dissolution of enfeebled or dead bodies. When the structure of a civilisation is rotten, it is always the masses that bring about its downfall. It is at such a juncture that their chief mission is plainly visible, and that for a while the philosophy of number seems the only philosophy of history. Is the same fate in store for our civilisation? There is ground to fear that this is the case, but we are not as yet in a position to be certain of it. However this may be, we are bound to resign ourselves to the reign of the masses, since want of foresight has in succession overthrown all the barriers that might have kept the crowd in check. We have a very slight knowledge of these crowds which are beginning to be the object of so much discussion. Professional students of psychology, having lived far from them, have always ignored them, and when, as of late, they have turned their attention in this direction it has only been to consider the crimes crowds are capable of committing. Without a doubt criminal crowds exist, but virtuous and heroic crowds, and crowds of many other kinds, are also to be met with. The crimes of crowds only constitute a particular phase of their psychology. The mental constitution of crowds is not to be learnt merely by a study of their crimes, any more than that of an individual by a mere description of his vices.