Having treated this subject at sufficient length, I shall not return to it now, but shall confine myself to saying a few words on the subject of such ideas as are accessible to crowds, and of the forms under which they conceive them. They may be divided into two classes. In one we shall place accidental and passing ideas created by the influences of the moment: infatuation for an individual or a doctrine, for instance. In the other will be classed the fundamental ideas, to which the environment, the laws of heredity and public opinion give a very great stability; such ideas are the religious beliefs of the past and the social and democratic ideas of to-day. These fundamental ideas resemble the volume of the water of a stream slowly pursuing its course; the transitory ideas are like the small waves, for ever changing, which agitate its surface, and are more visible than the progress of the stream itself although without real importance. At the present day the great fundamental ideas which were the mainstay of our fathers are tottering more and more. They have lost all solidity, and at the same time the institutions resting upon them are severely shaken. Every day there are formed a great many of those transitory minor ideas of which I have just been speaking; but very few of them to all appearance seem endowed with vitality and destined to acquire a preponderating influence. Whatever be the ideas suggested to crowds they can only exercise effective influence on condition that they assume a very absolute, uncompromising, and simple shape. They present themselves then in the guise of images, and are only accessible to the masses under this form. These imagelike ideas are not connected by any logical bond of analogy or succession, and may take each other's place like the slides of a magic-lantern which the operator withdraws from the groove in which they were placed one above the other. This explains how it is that the most contradictory ideas may be seen to be simultaneously current in crowds. According to the chances of the moment, a crowd will come under the influence of one of the various ideas stored up in its understanding, and is capable, in consequence, of committing the most dissimilar acts. Its complete lack of the critical spirit does not allow of its perceiving these contradictions.