What concept is Charles de Secondat, baron de Montesquieu best known for?

Charles de Secondat, baron de Montesquieu is best known for the concept of separation of powers, which he articulated in his influential work, "The Spirit of the Laws." Montesquieu argued that the political authority of a state should be divided into three branches: the legislative, the executive, and the judicial. This separation is designed to prevent any single branch from gaining too much power and to create a system of checks and balances where each branch can limit the powers of the others. This idea has had a profound impact on the development of modern democratic governments, particularly in the formation of the United States Constitution, where similar principles are embedded to ensure a balanced distribution of governmental powers.