Bill Greene writes,

While a major theme of this book is that a historical progress has bubbled up from the bottom — from the actions of the common men and women of history–a secondary theme is that most of history’s evils have come from the top–the intelligentsia, the organized groups, the soft-science experts who arise in mature societies and lead their nation’s decline.

Greene’s over-arching intellectual theory is that intellectuals with over-arching theories are a the chief threat to civilization. In William Easterly’s terms, ordinary people are Searchers, who try to improve things by trial and error. Intellectuals are Planners, whose grandiose attempts at top-down organization are doomed to failure, sometimes with a totalitarian mode of implementation in the process.