地震、宗教与意大利城市向自治的转型*

Abstract This article presents a unique historical experiment to explore the dynamics of institutional change in the Middle Ages. We have assembled a novel data set, where information on political institutions for northern central Italian cities between 1000 and 1300 is matched with detailed information on the earthquakes that occurred in the area and period of interest. Exploiting the panel structure of the data, we document that the occurrence of an earthquake retarded institutional transition from autocratic regimes to self-government (the commune) in cities where the political and the religious leaders were the same person (episcopal see cities), but not in cities where political and religious powers were distinct (non–episcopal see cities). Such differential effect holds for destructive seismic episodes and for events that were felt by the population but did not cause any material damage to persons or objects. Ancillary results show that seismic events provoked a positive and statistically significant differential effect on the construction and further ornamentation of religious buildings between episcopal and non–episcopal see cities. Our findings are consistent with the idea that earthquakes, interpreted in the Middle Ages as manifestation of the will and outrage of God, represented a shock to people’s religious beliefs and, as a consequence, enhanced the ability of political-religious leaders to restore social order after a crisis relative to the emerging communal institutions. This interpretation is supported by historical evidence.