Originally published in 1963, this classic book rethinks the history of Western political philosophy by contrasting classical-medieval principles against the "hypotheses" at the root of modern liberalism and conservativism. In Part I, "The Classical Christian Tradition from Plato to Aquinas," the author lays the foundation for a philosophical "structure" capable of producing "constitutional liberty." Part II, "The Modern Theory of Politics from Machiavelli to Marx," attempts to show, beginning with Machiavelli, the reversal and destruction of the pre-modern "structure" postulated in Part I. This classic volume on the origins of modern philosophical thought remains a standard in the field.