The development of the group spirit consists in two essential processes, namely, the acquisition of knowledge of the group and the formation of some sentiment of attachment to the group as such. It is essential that the group shall be apprehended or conceived as such by its members. Therefore the group spirit is favoured by whatever tends to define the group, to mark it off distinctly from other groups; by geographical boundaries; by peculiarities of skin-colour or of physical type, of language, or accent, of dress, custom, or habit, common to the members of the group; that is to say, by homogeneity and distinctiveness of type within the group.
And, though definition of the group as such within the minds of its members is the prime condition of the growth of the group spirit, that spirit will be the more effective the fuller and truer is the knowledge of the group in the minds of its members. Just as individual self-knowledge favours self-direction and wisdom of choice, so group self-knowledge must, if it is to be fully effective, comprise not only the conception of the group as a whole but also the fullest possible knowledge of the component parts and individuals and an understanding of their relations to one another. In this respect smallness and homogeneity of the group are obviously favourable. But knowledge of the group, however exact and widely diffused, is of itself of no effect, if there be not also widely diffused in the members some sentiment of attachment to the group. The prevailing group sentiment is almost inevitably one of attachment. There are exceptional instances in which men are compelled to act as members of a group which they hate or despise, notably in some cases of compulsory military service and in convict gangs; but it must be rare that, even under such conditions, some sense of common interest, some fellow feeling for other members in like distressing circumstances, does not lead to the growth of some group spirit, provided only that the group has some continuity and some homogeneity in essentials.
In all natural and spontaneously formed groups, the extension of the self-regarding sentiment to the group is a normal and inevitable process; and, like the self-regarding sentiment, the sentiment so formed may range from an insane and incorrigible pride (as often in the case of the family sentiment) to a decent self-respect that is perfectly compatible with a modest attitude and with reasonable claims upon and regard for the interests of other groups.