Such is the revulsion felt at the age, says Jonathan Glover in this study of 20th-century inhumanity, that ethics need to be completely rethought.

ECONOMIST: 20th-century history (2): ...then the ethics | The

Please try to remember that what they believe, as well as what they do and cause you to endure, does not testify to your inferiority but to their inhumanity and fear.

NPR: An Author's Companion in Rage, Exile and Return

And to this day, there are voices on America's political right that remain profoundly sceptical about the idea of costly pledges to wage wars in the name of protecting people from inhumanity.

ECONOMIST: Responsibility to protect

All too easily arrogance slides into inhumanity.

ECONOMIST: Population control

One can argue that it is not America's job to fix the world's problems, to stop the killings in distant lands even if, as we now know, those killings involve horrific weapons banned by international agreements that set a limit to our inhumanity even in times of war.

CNN: Obama, failing on moral leadership?