What are we to make of the 20th Century? Like any period it is marked with its glories and its horrors. In his now classic work Modern Times, historian Paul Johnson gives a sober assessment of the 20th century and estimates, many think conservatively, that 100 million died in war and for ideological reasons in that violent century. Perhaps no century can be said to have been bloodier.It was a century of the imposition of every sort of collectivism from communism, fascism, tribalism, and socialism , all with catastrophic results. Whole populations were the subject of social experiments; and here...