The political philosophy that places individual liberty, limited government, the rule of law, and equal rights at the center of political life — the foundational ideology of Western constitutional democracy, the intellectual tradition that produced both the American and French revolutions, and the framework within which the most consequential political arguments of the modern era have been conducted, even by those who reject it.
Liberalism is the water most of the modern world swims in. Constitutional democracy, freedom of speech, religious toleration, equality before the law, individual rights, free markets — these are liberal institutions, even when the people who inhabit them don't call them that. Understanding liberalism is understanding the default operating system of modern political life: where it came from, what problems it was designed to solve, why it has proved so durable, and why its critics — from the left, the right, and the communitarian center — find it insufficient.