We develop a dynamic network model of collective action that explains
how collective action can arise in the absence of selective incentives
or disincentives from the voluntary action of rational actors in larg
e groups. We show that the search for balance in social interaction am
ong interdependent actors can yield a cascade of activism and result i
n a successful social movement. The characteristics of actors critical
for movement success are identified. We also explore the structural c
onditions underlying a successful cascade of activism and thus identif
y the social dynamics of and the structural conditions for collective
action in human society.