Montesquieu 1689 – 1755

Charles-Louis de Secondat, Baron de Montesquieu, was a French philosopher and one of the architects of Enlightenment political thought. His Persian Letters satirized European customs through the eyes of imagined Persian travelers, while The Spirit of the Laws, the labor of two decades, articulated a sweeping comparative theory of forms of government and the conditions under which political liberty can flourish. His central thesis, that the powers of legislation, execution, and judgment ought to be separated, shaped the constitutional thinking of the American founders and the French Revolution alike.

Charles-Louis de Secondat, baron de la Brède et de Montesquieu (1689–1755) was a French Enlightenment political philosopher whose Spirit of the Laws is one of the founding works of modern comparative political philosophy and constitutional thought. Born to an old Bordeaux noble family, he served as président à mortier of the Bordeaux parlement before selling the position in 1726 and devoting himself to philosophical writing.

Montesquieu's first major work, the Persian Letters (1721), is a satirical philosophical novel in the form of correspondence between two Persians traveling in Europe — a wry comparative analysis of French institutions and customs through estranging foreign eyes. The book made Montesquieu's name. The Considerations on the Causes of the Greatness of the Romans and Their Decline (1734) developed the philosophical-historical method that the larger Spirit of the Laws (1748) deployed across all of human political experience.

The Spirit of the Laws develops the doctrine of the separation of powers — legislative, executive, and judicial — that shaped the American constitutional framework decisively, and the framework distinguishing republican, monarchical, and despotic forms of government by their animating principles. Montesquieu's comparative method — climate, geography, religion, history, and political culture as conditions of political form — anticipates much subsequent social science. He died in Paris in 1755.