It being impossible to study here all the successive degrees of organisation of crowds, we shall concern ourselves more especially with such crowds as have attained to the phase of complete organisation. In this way we shall see what crowds may become, but not what they invariably are. It is only in this advanced phase of organisation that certain new and special characteristics are superposed on the unvarying and dominant character of the race; then takes place that turning already alluded to of all the feelings and thoughts of the collectivity in an identical direction. It is only under such circumstances, too, that what I have called above the PSYCHOLOGICAL LAW OF THE MENTAL UNITY OF CROWDS comes into play. Among the psychological characteristics of crowds there are some that they may present in common with isolated individuals, and others, on the contrary, which are absolutely peculiar to them and are only to be met with in collectivities. It is these special characteristics that we shall study, first of all, in order to show their importance. The most striking peculiarity presented by a psychological crowd is the following: Whoever be the individuals that compose it, however like or unlike be their mode of life, their occupations, their character, or their intelligence, the fact that they have been transformed into a crowd puts them in possession of a sort of collective mind which makes them feel, think, and act in a manner quite different from that in which each individual of them would feel, think, and act were he in a state of isolation. There are certain ideas and feelings which do not come into being, or do not transform themselves into acts except in the case of individuals forming a crowd. The psychological crowd is a provisional being formed of heterogeneous elements, which for a moment are combined, exactly as the cells which constitute a living body form by their reunion a new being which displays characteristics very different from those possessed by each of the cells singly. Contrary to an opinion which one is astonished to find coming from the pen of so acute a philosopher as Herbert Spencer, in the aggregate which constitutes a crowd there is in no sort a summing-up of or an average struck between its elements. What really takes place is a combination followed by the creation of new characteristics, just as in chemistry certain elements, when brought into contact--bases and acids, for example--combine to form a new body possessing properties quite different from those of the bodies that have served to form it. It is easy to prove how much the individual forming part of a crowd differs from the isolated individual, but it is less easy to discover the causes of this difference.