What prompted Voltaire to speak of a "century of Frederick," which even the King of Prussia was not willing to accept, and why did Kant still refer to the 18th century as a "century of Frederick"? From a comparative perspective and based on extensive source studies, Claudia Schröder compares the positions of French Enlightenment figures like Voltaire and d'Alembert with those of German writers, historians, and politicians, particularly those of King Frederick II of Prussia, Herder, Kant, and the Prussian minister Hertzberg. It is demonstrated how the disputes between classicist admirers of antiquity and modernist Enlightenment thinkers - the Querelle des anciens et des modernes - in France led to the development of an understanding of Enlightenment progress that also resulted in a new conception of history in Prussia: the idea.