Born in 1689, Montesquieu came from a noble family and was educated in law. His early career included service as a magistrate, which exposed him to the workings of the legal system and provided firsthand experience with the exercise of power. This practical knowledge informed his later philosophical work, as he sought to understand the connections between law and society, as well as the impact of political structures on individual liberty.
In The Spirit of Laws, Montesquieu examined a wide variety of political systems, including republics, monarchies, and despotisms, and their corresponding legal frameworks. His most famous contribution to political thought was his theory of the separation of powers, in which he argued that to prevent tyranny, government power should be divided into distinct branches—executive, legislative, and judicial—each with separate functions and the ability to check the other branches. This framework has become a central tenet of modern democratic systems, including the U.S. Constitution.