Lagrange’s Mathematical Life in Berlin and Paris. A Reappraisal

Lagrange’s life was marked by three distinct periods in three European capitals: Turin, Berlin and Paris. Lagrange left Turin, his hometown, due to the lack of prospects for an adequate scientific career. As is well known, his dissatisfaction came to the notice of d’Alembert, who promoted his transfer to Berlin, after a place was vacated by Euler at the Academy of Sciences and Letters. After twenty years dedicated to intense research, Lagrange’s quiet life in Berlin came to an end with the death of Frederick II of Prussia, so he accepted a position at the Academy of Sciences in Paris. Lagrange’s time in Turin has, by now, been well studied and documented, as have the why and wherefore of his transfers. There is also an extensive body of literature on his Parisian period. However, as to his Berlin period, which is well illustrated by his vast scientific production, little is still known as regards his interaction with the Academy and the events of the Prussian court. The main part of this work is dedicated to this period, starting from the end of the Turin period up to his first decade in Paris. The usual representation of a Lagrange engaged exclusively in his mathematical research has undergone a thorough revision.