Relatively rare but historically important events in which an entire social and political order is overturned, usually by violent means, and reconstructed on new principles with new leaders. The word revolution has come to be applied loosely to any dramatic social change—as in ‘industrial revolution’, ‘computer revolution’, ‘style revolution’, and so forth. But its central meaning is still political. It is difficult to make a sharp distinction between a political revolution and a rebellion, although some have argued that the term ‘revolution’ should be reserved for those instances in which the new governing elite attempts to make fundamental changes in the social structure of the post-revolutionary society, whereas rebellions are more limited political upheavals involving only the replacement of one ruling group by another. On this criterion, rebellions clearly shade into revolutions, depending upon one's judgement as to the scope and intensity of the social changes that follow the seizure of power.
The prototypes of all modern revolutions were the American and French Revolutions of 1776 and 1789. Both had a clear political agenda, and both resulted in a complete transformation of power relationships. In this century, the Russian Revolution of 1917 and the Chinese Revolution of 1948 had similar dramatic results. Not all revolutions in recent history have been socialistic or egalitarian, or even modernizing; many have been anti-democratic or right-wing. Fundamentalist Islam has swept through the Middle East, most notably in the revolutionary downfall of the Shah of Iran in 1979. The 1990s have witnessed a ‘reverse revolution’ in many former communist states.
Probably the most influential theory of revolution in sociology has been the historical materialism of Karl Marx and Friedrich Engels. However, it should be recognized that Marxism has come to embody several (by no means compatible) theories of revolution, including for example the theory of the dictatorship of the proletariat advanced by Lenin and of peasant revolution proffered within Maoism. Many subsequent sociological studies of revolutionary change are explicit critiques of the Marxist view of history in general and of revolutions in particular.
Most studies of rebellions and revolutions have necessarily been historical, and have focused on causes and processes. Theories that stress social disequilibrium, rising expectations, and relative deprivation are plausible, but have not proved highly explanatory or predictive. In more recent work, Theda Skocpol has formulated a theory of revolution which stresses the inability of institutions to cope with normal crises (States and Social Revolutions, 1979), and Charles and Louis Tilly have proposed a historical model in which rebellions arise opportunistically out of a shifting balance of power and resources (The Rebellious Century 1830—1930, 1975). Skocpol's theory was particularly controversial. She proposes a macro-level, structural analysis, which makes a sharp distinction between political revolutions (leadership changes) and social revolutions (which transform the whole of society). Arguing against monocausal explanations of social revolutions (for example rising expectations, class conflicts) she proposes a complex, fluid model which emphasizes the differences between states, the role of external factors such as international economic competition, and the availability of grievance channels for different social classes. (This focus on the complexity of revolutionary social change is continued in her later work, including her edited and co-edited volumes on Vision and Method in Historical Sociology, 1984, and Bringing the State Back In, 1985.)