Montesquieu

Montesquieu was a nobleman from near Bordeaux who studied law and inherited from an uncle both a barony and the presidency of the Bordeaux parlement. In 1721 he published anonymously the Persian Letters, satirising French religion, politics and manners through the eyes of two Persian travellers, and became famous overnight. He sold his judicial office, entered the Académie française, and travelled Europe for three years, spending eighteen months in England studying its parliamentary system.

Back at La Brède he spent twenty years on The Spirit of the Laws, nearly losing his sight in the process. Published in 1748, it went through twenty-two editions in two years and was placed on the Index. Its question is not what the best regime is but why the laws of nations differ so much. The answer: laws are necessary relations arising from the nature of things, shaped together by form of government, climate, soil, religion, commerce and custom, and the 'spirit of the laws' is the sum of these relations.

He divided governments into republics, monarchies and despotisms, each with its own principle: virtue, honour and fear. The most famous chapter concerns the English constitution: liberty exists only where legislative, executive and judicial powers are separated and check one another, because everyone who has power tends to abuse it until he meets limits. The framers of the American constitution cited him constantly; he was the most quoted author at the Philadelphia convention.