It may be that the best book that will ever be written about today’s progressive mind-set was published in 1941. That in The Red Decade author Eugene Lyons was, in fact, describing the Communist-dominated American Left of the Depression-wracked 1930s and 1940s makes his observations even more meaningful, for it is sobering to be confronted with how little has been gained by hard experience. The celebration of feelings over reason? The certainty of moral virtue? The disdain for tradition and the revising of history for ideological ends? The embrace of the latest definition of correct thought? Lyons was one of...