There are five conditions of principal importance in raising collective mental life to a higher level than the unorganised crowd can reach, no matter how homogeneous the crowd may be in ideas and sentiments nor how convergent the desires and volitions of its members. These are the principal conditions which favour and render possible the formation of a group mind, in addition to those more fundamental conditions of collective life which we have noted in the foregoing chapter. The first of these conditions, which is the basis of all the rest, is some degree of continuity of existence of the group. The continuity may be predominantly material or formal; that is to say, it may consist either in the persistence of the same individuals as an intercommunicating group, or in the persistence of the system of generally recognised positions each of which is occupied by a succession of individuals. Most permanent groups exhibit both forms of continuity in a certain degree; for, the material continuity of a group being given, some degree of formal continuity will commonly be established within it. The most highly organised groups, such as well-developed nations, exhibit both forms in the highest degree. A second very important condition, essential to any highly developed form of collective life, is that in the minds of the mass of the members of the group there shall be formed some adequate idea of the group, of its nature, composition, functions, and capacities, and of the relations of the individuals to the group. The diffusion of this idea among the members of the group, which constitutes the self-consciousness of the group mind, would be of little effect or importance, if it were not that, as with the idea of the individual self, a sentiment of some kind almost inevitably becomes organised about this idea and is the main condition of its growth in richness of meaning; a sentiment for the group which becomes the source of emotions and of impulses to action having for their objects the group and its relations to other groups. A third condition very favourable to the development of the collective mind of a group, though not perhaps absolutely essential, is the interaction (especially in the form of conflict and rivalry) of the group with other similar groups animated by different ideals and purposes, and swayed by different traditions and customs. The importance of such interaction of groups lies chiefly in the fact that it greatly promotes the self-knowledge and self-sentiment of each group. Fourthly, the existence of a body of traditions and customs and habits in the minds of the members of the group determining their relations to one another and to the group as a whole.