Demonstrating joint sufficiency requires studying cases where one cause is absent

Evidence

Skocpol is explicit that these two causes are jointly—not individually—sufficient for social revolutions. This is clear from her assertion that the two factors “were, taken together, the sufficient distinctive causes” and from her explicit remarks that state breakdowns would not have led to social revolutions without peasant revolts (1979, 112). Elsewhere, by examining cases of non–social revolution in which only one of the two conditions was present, she attempts to empirically demonstrate that neither condition is by itself enough to produce social revolution. — Gary Goertz, Social Science Concepts and Measurement, 1548