tegration to the last
this law is illustrated. Likeness in the units forming a social group
being one conditioned to their integration, a further condition is their
joint reaction against external action: co-operation in war is the chief
cause of social integration. The temporary unions of savages for offence
and defence show the initiatory steps. When many tribes unite against a
common enemy, long continuance of their combined action makes them
coherent under some common control. And so it is subsequently with still
larger aggregates.

DIFFERENTIATION

The state of homogeneity in the social aggregate is an unstable one. The
primary political differentiation originates from the primary family
differentiation. Men and women very early respectively form the two
political classes of rulers and ruled. The slave class acquires
separateness only as fast as there arrives some restrictions on the
powers of the owners; slaves begin to form a division of the body
politic when their personal claims begin to be distinguished as limiting
the claims of their masters. Where men have passed into the agricultural
or settled state it becomes possible for one community to take
possession bodily of another community, along with the territory it
occupies. When this happens, there arise additional class divisions. The
class differentiation of which militancy is the actual cause is
furthered by the establishment of definite descent, especially male
descent, and by the transmission of position and property to the eldest
son of the eldest continually. Inequalities of position and wealth once
initiated tend to increase and to establish physical differences; and
beyond these there are produced by the respective habits of life mental
differences, emotional and intellectual, strengthening the general
contrast of nature. When there come conquests which produce compound
societies and doubly compound ones there result superpositions of ranks:
while the ranks of the conquering society become respectively higher
than those which have existed before, the ranks of the conquered society
become respectively lower. The political differentiations which
militancy originates and which for a long time increase in definiteness,
are at later stages and under other conditions interfered with,
traversed, and partially or wholly destroyed. While the higher political
evolution of large social aggregates tends to break down the divisions
of rank which grew up in th