British parliamentarian and historian Lord Acton is famous for his 1887 pronouncement, in a letter to the Bishop of London, Mandell Creighton, that "power tends to corrupt, and absolute power corrupts absolutely".
Many of you, however, may not have heard the words following that sentence: "Great men are almost always bad men, even when they exercise influence and not authority, still more when you add the tendency or the certainty of corruption by authority."
It's a much debated question of history - do you have to be bad to be great? - and it's one that begins with how you define the word "great".
I'm sure many of us would claim to know great men or women in our lives, but I'd wager almost none of them will be discussed outside a very obscure group (their relatives) in 100 years.
In 1000 years? Well, I'll go out on a limb and say none of the people you consider great will be remembered, analysed or discussed by English speakers, let alone students of languages other than English, from non-Western cultures.
If you apply that criterion, the great men (and women) of history is a pretty select group.
You'd have to throw Jesus in there, Mohammed, Confucius, Buddha, then I'd wager dudes like Alexander the Great (he does have the right name), Julius Caesar, Genghis Khan, Napolean, Atilla the Hun and Hitler would make the top 100.
This is not to say men like Johannes Gutenberg (the inventor of the printing press), Ts'ai Lun (the Chinese official who invented paper), Pasteur, Galileo, Euclid, Darwin, Marx and Newton wouldn't get a guernsey, it's just they don't roll off the tongue of your average person in the street.
In that sense, many people are influential - such as the inventor of the World Wide Web Tim Berners-Lee, as well as historical figures as diverse as Copernicus, Lavoisier, Faraday, Edison, Marconi and Daguerre. But "great"?
Popular history and philosophy broadcaster Dan Carlin poses this question in one of his enormously entertaining Hardcore History podcasts when he asks: "Would you be willing to order the killing of an innocent woman or child?"
"If you said you would not be willing to do that, you are already off the potential 'great person' list - at least in terms of world leaders," Carlin says
"Even the most humanistic world leaders, when it comes to their personal outlook, a guy like Jimmy Carter, who was a president who was so humanistic he had a hard time doing his job sometimes.
"Here's a guy who was probably responsible for less deaths as an American president than any other president I can think of in modern times and there's still, certainly, quite a few people who died because Jimmy Carter made a decision one way or the other."
He makes the sobering point, however, that men like Alexander, Caesar, Genghis Khan, Napoleon and Hitler killed millions but the only difference between the first four names on that list and the Nazi leader is people are still alive who remember those murdered by Adolf.
The millions killed by Alexander, Caesar and Genghis Khan? They're just historical statistics.
I'm in no way trying to justify or glorify Hitler's obvious madness and genocide. I just think it's interesting how the passage of time allows us to elevate men to the level of "great", simply because they did horrific and catastrophic things on a scale never before seen, to people we have no emotional connection to, i.e. the long dead.
Simone Weil, the French philosopher described by Albert Camus as "the only great spirit of our times" and who died during World War II of tuberculosis, made the point in 1940: "If Germany, thanks to Hitler and his successors, were to enslave the European nations and destroy most of the treasures of their past, future historians would certainly pronounce that she had civilized Europe."
I guess the secret is that if you're gonna kill millions, you better win the war.
The most obvious thing that jumps out at you when you put a list like this together is the absence of female names, which some might argue has to do with their historical exclusion and marginalisation, particularly when it came to leadership roles.
Except it doesn't really hold up.
Toregene Khatun was the Regent Empress of the Mongol Empire from 1242–1246 after the death of her husband, the Great Khan, Ogedei, third son of Genghis. She was easily the most powerful person in the world at that time and probably the most powerful woman in all of human history.
She had, perhaps, the greatest military force the world had ever seen at her disposal and controlled the majority of the two most advanced civilisations in the world at that time, China and Islam.
She was also, no doubt, a rape victim, having been "given" to Ogedei after her clan, the Merkits, was vanquished by Genghis.
That's another cute thing about history - woman are routinely described as being "given" or "becoming wives" after their families and friends have been murdered by their new husbands.
Some honeymoon, eh?
However, despite Toregene's indisputable significance, she's largely disappeared from history; you'd probably have never heard of her unless you were a Mongol history buff.
So, I guess, the other secret to being "great" and killing millions, is you not only better win the war, but be a man, too.