Enlightenment ideas challenge the old order

For most of history, kings and queens claimed to rule by divine right -- the idea that God himself had placed them on the throne, so questioning the monarch meant questioning God. That claim started to crack in the 1600s, when the Scientific Revolution taught Europeans to trust observation and reason over inherited authority. If Copernicus could overturn 1,400 years of accepted teaching about the earth's place in the universe, and if Isaac Newton could explain the motion of every planet with a few mathematical laws in his 1687 Principia, then maybe reason could also reveal better ways to organize government and society. A group of thinkers historians call the philosophes took that leap, and the result -- the Enlightenment -- would topple thrones within a century.

English philosopher John Locke argued in his 1689 Two Treatises of Government that people are born with natural rights -- life, liberty, and property -- that no king grants and no king may justly take away. Government, Locke wrote, exists only because people consent to it in a social contract, and if a government violates those rights, the people have a right to overthrow it. The French baron Montesquieu proposed splitting government into separate legislative, executive, and judicial branches so no single person could seize all the power. Jean-Jacques Rousseau argued that legitimate authority flows only from the "general will" of the people, and Voltaire spent his career attacking censorship and religious intolerance. These were not abstract classroom ideas: pamphlets and salon conversations carried them across Europe, and colonists in British North America were reading Locke closely by the 1770s.