Taking inspiration from René Descartes,[1] and based on texts of ancient historians and poets, Fustel investigates the origins of the most archaic institutions in the Greco-Roman world.

Over time, need has led men to regularize and make more consistent their relations with one another, and the rules that govern the family were transferred to increasingly larger units called gens, arriving eventually at the city-state.

Therefore, the origin of the city and of private property is also religious, as is witnessed by the practice of lustration, a periodic purification ceremony in connection with the census of all citizens, and by the public banquets in honor of local gods.

The laws originally encoded the privileges of the aristocracy, causing great discomfort to the plebs and a social revolution in which the common well-being of society became the new basis of religion.

When he revised the book in 1875, his modifications were very slight, and it is conceivable that, had he recast it, as he often expressed the desire to do in the last years of his life, he would not have abandoned any part of his fundamental thesis.