The 20th century is often described as the most bloody in humanhistory, but rarely are the red drops as carefully catalogued as inJonathan Glover's "Humanity: A Moral History of the Twentieth Century."Less a history book than a study in applied ethics, Glover attempts toanalyze what remains of the Enlightenment after the gore of the past 100 years. The French Revolution, Rwanda, Nazi Germany, Soviet Russia,Hiroshima, World War I--Glover cringes from each of these in turn.

"Humanity" is ultimately little more than acompendium of conventional wisdom. Glover offers little clear explanationof why these atrocities happened, content with describing them as theoutcome of a disastrous meeting between the darker aspects of "psychology"and new destructive technologies. Even his moral lessons are confusing yetpredictable; he observes that having a strong sense of identity can helppeople resist committing terrible acts, yet that at times a strongidentity can actually be forged in the commission of horrors. Religionplays a minor role in his analysis; problems of character are consideredin terms of identity rather than faith. More attention to the history ofthese terrible regimes--rather than simply repeating how terrible theywere--would have deepened not only the historical but the moral weight ofGlover's book.