Sidney Tarrow (1998) defines them as "a phase of heightened conflict across the social system", with "intensified interactions between challengers and authorities which can end in reform, repression and sometimes revolution".
Tarrow argues that cyclical openings in political opportunity create incentives for collective action.
When the political opportunity disappears, for example because of a change in the public opinion caused by a rise in insecurity and violence, the movement dissolves.
It demands that states devise broad strategies of response that are either repressive or facilitative, or a combination of the two."
This has however changed in the 18th century, when social movements evolved in West Europe and North America (see also works by Charles Tilly).