The Ancien Régime was the feudal system in Europe from the 15th to 18th centuries characterized by absolute monarchs, a stratified society of nobles, clergy, and commoners, and a rural agrarian economy. During this time, Enlightenment thinkers advocated for reason and scientific progress to criticize the traditions and injustices of the Ancien Régime, laying the foundations for liberalism, individual rights, and new economic theories that would contribute to revolutionary changes.