Weaver’s book offers human liberty as the “mainspring of human progress.” The book begins with a series of puzzles about why we are so much better off than our ancestors and then explores why systems lacking liberty haven’t worked. The bulk of the book is an historical look at how the “revolutionary” idea of liberty struggled to dominate and eventually did. Weaver finishes with a discussion of the “fruits of freedom” as seen from the late 1940s.