Montesquieu, Charles Louis de Secondat, Baron de la Brède (1689–1755)

French philosophical historian, author of Lettres persanes/Persian Letters (1721). De l'Esprit des lois/The Spirit of the Laws (1748), a 31-volume philosophical disquisition on politics and sociology as well as legal matters, advocated the separation of powers within government, a doctrine that became the basis of liberal constitutions.

Montesquieu arrived at the concept of the separation of powers – that is, of the legislative, executive, and judicial functions – from the viewpoint of the Tory opposition to Robert Walpole and the Whigs in the UK, where he lived 1729–31.

Born near Bordeaux, Montesquieu became adviser to the Bordeaux parliament 1714. After the success of Lettres persanes, which satirizes French legal and political institutions, he adopted a literary career, writing Considérations sur les causes de la grandeur des Romains et de leur décadence/Considerations on the Greatness and Decadence of the Romans 1734.