I'm not exactly sure what to do with this, or how it might lend itself to discussion, but I thought I'd offer up a small passage from the second section of "Some Questions of Moral Philosophy" as a singularly concise and direct distillation of the ideas that inform most of the essay in the book. The quote comes from pages 94 and 95, if anyone wants to examine the context.
Hannah Arendt wrote:
Philosophy (and also great literature, as I mentioned before) knows the villain only as somebody who is in despair and whose despair sheds a certain nobility about him. I am not going to deny that this type of evildoer exists, but I am certain that the greatest evils we know of are not due to him who has to face himself again and whose curse he cannot forget. The greatest evildoers are those who don't remember because they have never given thought to the matter, and, without remembrance, nothing can hold them back. For human beings, thinking of past matters means moving in the dimension of depth, striking roots and thus stabilizing themselves, so as not to be swept away by whatever may occur -- the Zeitgeist or History or simple temptation. The greatest evil is not radical, it has no roots, and because it has no roots it has no limitations, it can to unthinkable extremes and sweep over the whole world.
Encapsulated in this brief passage are both the occasion for Arendt's essays -- the sort of ordinary but momentous evildoer made emblematic by Adolf Eichmann -- and also the basic elements of her attempt to answer the problem posed by such people.