Any thoughtful observer of political and social discourse is forced to note the ironies and disjuncts in specific beliefs from time to time. Conservatives often support restrictions on behavior in order to effect security, while liberals preach freedom but are happy to truncate it in order to marshall the resources to support their favored victim classes. Either side, if honestly introspective, ought to be troubled about why this is. Thomas Sowell, one of America's most thoughtful and intellectually honest commentators explains just why this is and traces the origin of the question to the Enlightenment and post-enlightenment thinkers before and shortly after the French Revolution. He describes the key dichotomy as between the "constrained" and "unconstrained" views of human nature, which view mankind as flawed or perfectable, respectively. Another author describing comparable distinctions in international relations, Robert Kaplan, uses the terms Realist and Idealist to discuss the same cleavage. In setting this out, Sowell manages to produce a genuinely Aristotelian approach to modern thought that is extremely worth reading. What's more, he does all of this in a very readable, approachable prose that it more enjoyable to read than any text on such deep subjects ought to be. It's one of the very few books that improves the reader while giving pleasure in doing so.