They sensed that what had happened around them and in their presence, and in them, was irrevocable. Never again could it be cleansed; it would prove that man, the human species - we, in short - had the potential to construct an enormity of pain, and that pain is the only force created from nothing, without cost and without effort. It is enough not to see, not to listen, not to act.
Primo LeviWe will not return No one must leave here and so carry to the world, together with the sign impressed on his skin, the evil tidings of what man's presumption made of man in Auschwitz
Primo LeviPerhaps one cannot, what is more one must not, understand what happened, because to understand [the Holocaust] is almost to justify...no normal human being will ever be able to identify with Hitler, Himmler, Goebbels, Eichmann, and endless others. This dismays us, and at the same time gives us a sense of relief, because perhaps it is desirable that their words (and also, unfortunately, their deeds) cannot be comprehensible to us. They are non-human words and deeds, really counter-human.
Primo LeviIn order for the wheel to turn, for life to be lived, impurities are needed, and the impurities of impurities in the soil, too, as is known, if it is to be fertile. Dissension, diversity, the grain of salt and mustard are needed: Fascism does not want them, forbids them, and that's why you're not a Fascist; it wants everybody to be the same, and you are not. But immaculate virtue does not exist either, or if it exists it is detestable.
Primo Levi