=3. Struggles for Mastery or Liberty.=--In most cases these cannot be separated from economic struggles. Masters and slaves were in economic as well as personal relations, and nearly all class contests on a large scale have had at least one economic root, whatever their other sources. But the economic is not their only root. There have been wars for glory or for liberty as well as for territory or booty or slaves. As the struggle for existence has bred into the race the instinct of self-defense with its emotion of anger, the instinct to rivalry and mastery, and the corresponding aversion to being ruled, so the progress of society shows trials of strength between man and man, kin and kin, tribe and tribe. And while, as stated in the preceding chapter, the coöperation made necessary in war or feud is a uniting force, there is another side to the story. Contests between individuals show who is master; contests between groups tend to bring forward leaders. And while such masterful men may serve the group they are quite as likely to find an interest in opposing group customs. They assert an independence of the group, or a mastery over it, quite incompatible with the solidarity of the kinship clan, although the patriarchal type of household under a strong head may be quite possible. There comes to be one code for rich and another for poor, one for Patricians and another for Plebs, one for baron and another for peasant, one for gentry and another for the common folk. For a time this may be accepted patiently. But when once the rich become arrogant, the feudal lord insolent, the bitter truth is faced that the customs have become mere conventions. They no longer hold. All the old ties are cast off. The demand for freedom and equality rises, and the collision between authority and liberty is on.