From Newton's laws to Locke's natural rights — how the Scientific Revolution's confidence in reason and observation reshaped politics, religion, and economics. Meet the philosophes who challenged absolute authority, and the "enlightened" monarchs who tried to co-opt their ideas.
Six ways to master Unit 4 — pick whichever fits how you like to study.
Six topics from the College Board CED, in order.
Unit 4 traces how the confidence and method of the Scientific Revolution spilled over into politics, religion, and economics. Isaac Newton's Principia synthesized a century of scientific inquiry into a single, elegant system of universal laws — and convinced European thinkers that reason and observation, not tradition or revelation, were the surest path to truth. Philosophes like Locke, Voltaire, Montesquieu, and Rousseau applied that same confidence to government and society, producing theories of natural rights, separation of powers, and the social contract that would underpin later revolutions.
These ideas spread through salons, the printed page, and a transnational Republic of Letters, reaching educated elites across the continent. Some rulers — Frederick the Great of Prussia, Catherine the Great of Russia, and Joseph II of Austria — tried to apply Enlightenment reforms from the top down without giving up centralized authority, a pattern historians call enlightened absolutism. Meanwhile, Adam Smith challenged the mercantilist consensus with a new theory of free-market economics. This unit is roughly 10–13% of the AP European History exam, and its ideas directly set the stage for the political revolutions of the late 18th century.
The College Board ties Unit 4 to four of its course-wide themes: