The eighteenth century saw two great social revolutions, one in America, the other in France. One of them-the American Revolution-was the outcome of Enlightenment ideas, and was fueled, in particular, by the ideas of John Locke. The other-the French Revolution-was the outcome of anti-Enlightenment ideas, and was fueled , in particular, by two ideas of Jean Jacques Rousseau. These lectures will contrast the ideas of Locke with those of Rousseau, in order to explain the contrast in what these revolutions produced: a free and prosperous America, and a blood-soaked, tyrannical France. These lectures, therefore, will offer a case study in the power for good, of true philosophical ideas, and the destructiveness of false ideas.