What was the Enlightenment? Historians have drawn a picture in which the times and rhythms of its various instances are different, as are its ideals and objectives. Yet common characteristics can be identified, from Edinburgh to Milan or Paris. When Cesare Becarria and Alessandro Verri arrived in Paris, they felt at home in the salons of d'Holbach and Helvétius, just as David Hume felt at home at the same period in the same salons. What these intellectuals had in common was their intellectual identity as philosophes, whether from Scotland or Italy. If we wish to study the development of the Enlightenment, however, the model case remains that of France.

In 1750–1 the French government, led by Machault, aware of the crisis the state was going through, contrived a reform programme of which the main lines remained central for all subsequent governments. In 1751 the first volume of the Encyclopédie was published. Diderot and d'Alembert planned and realised this gigantic work in order to radically transform the mental, social and political structures of France. Here were two different and independent approaches to solving the crisis of the French state. Enlightenment and politics found themselves in a relationship of simultaneous independence and mutual support in a long article by Diderot entitled ‘Autorité politique’, in which he idealised the group of wise men who, aware of their role, their nature and their differences, surrounded and advised the good king Henry IV.