mited.
They must be characterized also by internal solidarity. Their membership
is stable because to break the bond of blood is not only to make one's
self an outcast but is also to be unfaithful to the ancestral gods; to
change one's religion is not only to be impious but is also to commit
treason; to expatriate one's self is not only to commit treason but is
also to blaspheme against high heaven.

But when associations of believers or of persons holding in common any
philosophy or doctrine whatsoever are no longer self-sufficing
communities, and when nations composite in blood have become compound in
structure, all social groups, clusters, or organizations, not only the
cultural ones drawn together by formative ideas, but also the economic
and the political ones, become in some degree plastic. Their membership
then becomes to some extent shifting and renewable. Under these
circumstances any given association of men, let it be a village, a
religious group, a trade union, a corporation, or a political party, not
only takes into itself new members from time to time; it also permits
old members to depart. Men come and men go, yet the association or the
group itself persists. As group or as organization it remains
unimpaired.

The economic advantage secured by this plasticity and renewableness is
beyond calculation enormous. It permits and facilitates the drafting of
men at any moment from points where they are least needed, for
concentration upon points where they are needed most. The spiritual or
idealistic advantage is not less great. The concentration of attention
and of enthusiasm upon strategic points gives ever-increasing impetus to
progressive movements.

Let us turn now from these merely proximate causes and effects of group
formation to take note of certain developmental processes which lie
farther back in the evolutionary sequence and which also have
significance for our inquiry, since, when we understand them, they may
aid us in our attempt to answer the question, What kind of group-making
is likely to be accomplished by cultural conflicts from this time forth?

The most readily perceived, because the most pictorial, of the conflicts
arising between one belief and another are those that are waged between
beliefs that have been localized and then through geographical expansion
have come into competition throughout wide frontier areas. Of all such
conflicts, that upon which the world has now fully entered bet