...The Holocaust disturbs us so deeply because it demonstrates that none of the things we associate with the advancement of civilization--peace, prosperity, industrialization, education, technological achievement--free us from the dark side of the human soul. Just as there is evil in the heart of every man, there is evil at the heart of even the most "civilized" human society. It is a humbling recognition. Man and society are both capable of the most appallingly depraved behavior. Only in the case of society, it occurs on an industrial scale.

The lives lost in the firebombing of Dresden or the nuclear flash over Hiroshima are no less significant, and the military choices that brought about those deaths remain profoundly disturbing, but they at least took place in the context of war. Whole societies were caught up in a life-or-death struggle.

What the Holocaust demonstrates is the danger of a one-party state. It shows what can happen when a group of true believers, convinced of the superiority of their own ideas, have unchecked power. They are then free to rewrite history to suit their political ends, and crush those who disagree or protest . . . or who worship God in a different way.

Like, say, the mullahs in Iran.