The French Revolution was, by any reckoning, one of the great defining episodes in the history of modernity. Whether one sympathizes with or reviles the aspirations, endeavours, and consequences of the Revolution, no one can doubt the immensity of the changes it wrought. Above all, the Revolution overtly challenged the three principal pillars of medieval and early modern society—monarchy, aristocracy, and the Church—going some way to overturning all three. Inevitably in the context, ideology—and linked to ideology, radical philosophy and political thought—were prime factors in the complex of pressures and impulses which shaped the Revolution. To question whether ideas and books can in fact cause revolutions and dislodge kings, a favourite historiographical pastime of recent years, may sound astute momentarily but on a closer view seems as shallow as the notion that great events in history may well have small, short-term, accidental, and unnecessary causes. Matching cause and effect is the essence of scientific logic. It is surely also the essence of meaningful historical interpretation.
A revolution of fact which demolishes a monarchical courtly world embedded in tradition, faith, and a social order which had over many centuries determined the distribution of land, wealth, office, and status seems impossible, or exceedingly implausible, without a prior revolution in ideas—a revolution of the mind—that had matured and seeped its way through large sections of society over a long period before the onset of the revolution in actuality. Claims that just such an upheaval of the mind had indeed paved the way were common in the years preceding the Revolution—as well as during the revolutionary years and the succeeding period through to the early nineteenth century. There is much room for debate about the precise nature of this revolution in ideas. One might, for instance, argue that only after 1750 did the philosophes change the mental map of Europe. One might quarrel with the diagnosis of a Rotterdam predikant who, the year before the outbreak of the Revolution, described his century as one in which authority, tradition, and faith had already largely been swept away by 'philosophy' propounded by 'a whole host of Spinozisten, Deurhofisten, Hattemisten, Leenhofisten, Naturalisten, Materialisten, Deisten, Atheisten, Vrijgeesten "freethinkers" and Sociniaanen with which weeds not only England, France and Germany but also our republic are strewn' and his identifying Spinoza as