A reflection on the history of humanism and the relationship of this philosophical tradition to the rise of totalitarianism in the 20th century. There are reveiws of arguments about what makes a man human, tracing the arguments from Plato and Aristotle to Sartre and Hannah Arendt. How was it possible for a great philosophical tradition, celebrated for affirming the unity of mankind, to end up inspiring political systems of such dehumanizing proportions? The book contrast eyewitness accounts with ideological justifications of the mechanized carnage of World War I, the horrors of concentration camps (Nazi and Soviet), and the campaigns of ethnic cleansing that continue in many parts of the world. Then it reveals how inadequate our so called humanitarian responses to these atrocities have been.