This week saw International Holocaust Remembrance Day, the annual event which commemorates the liberation of Auschwitz concentration camp.
It happened 70 years ago, on January 27 - a long time ago - but still has the power to shock you to the core. That power has endured; and as long as human beings have brains and hearts, it will continue to shock.
The BBC website put up audio footage from the Home Service of that era: reports from Auschwitz and other death-camps. In one, we had the clipped RP tones of Richard Dimbleby, the first broadcaster to enter Belsen, contrasted with the very obvious horror in his voice, at what he was witnessing.
The quintessential unflappable English chap, Dimbleby broke down more than once. The BBC, apparently, refused to air the report at first; they simply couldn't believe that people could do this. Back in modern times, BBC World Service's Newshour (9.05pm) had a comprehensive review of the subject, including an examination of why Israel, ironically, doesn't mark International Holocaust Remembrance Day, a report from Auschwitz, and interviews with survivors. One suggested adding an 11th Commandment: "Thou shalt not be a bystander."
That's the crucial question, isn't it - how exactly did this happen? The Nazis were a bunch of vicious lunatics, certainly. But how did a country of 50 million wholeheartedly "get with the programme?" It's unfortunate that, since World War II, people often automatically associate "German" with "Nazi", but the Third Reich was a brief, if seismic, hiatus of madness and barbarity in a long history of music, philosophy, science, reason.
It's a heavy cross for the German people to bear, yet bear it they have, and continue to do. The Pat Kenny Show (Newtsalk, Mon-Fri 10am) gave a fascinating insight into the impact of Holocaust history on Germans.
Georg Grote, a lecturer in the School of Languages and Literature at UCD, was born in the mid-1960s. So, like all post-war Germans, he was educated fully on the crimes of his forebears.
"Some things will never go away," he said at one point, "and should never go away. There can be no German identity without Auschwitz."
Georg kept emphasising one word: responsibility. The German people had a moral imperative to take responsibility for what some - not all, of course - had done; and more importantly, to make sure it never happened again.
In fairness, has there ever been a country which so thoroughly tried to atone for its sins? Every large nation has blood on its hands; the Germans, at least, openly admit it, and strive honourably to make amends.