What conditions the chances of liberty, wealth, and equality at the start of the third Christian millennium? Why did human civilizations develop so slowly for thousands of years, and then transform themselves during the last three hundred? This study of four great thinkers who lived between 1689 and 1995 -- Montesquieu, Adam Smith, De Tocqueville, and Ernest Gellner -- weaves their lives and works together and through their own words shows how they approached the question of the nature of humanity, our past and our future.