JOHANNESBURG - For US President Barack Obama and millions of people around the world, Nelson Mandela was a hero. But what are heroes? Why do we need them? And will there be another Mandela, or is he the last of a breed?
Delving into these questions means starting with the word itself.
"Hero" is charged with mythology: it is rooted in the ancient Greek term for demi-gods like Achilles.
In more modern times, the term came to describe mere mortals credited with exceptional qualities, such as Gandhi, Mother Teresa, Winston Churchill or Martin Luther King.
But it may also be used for fictional characters like James Bond or Superman, even athletes who achieve a remarkable feat.
This semantic stretch is a good indicator of our craving for super humans. "Heroism is a central concept of culture and society," said Frank Farley, a lecturer at Temple University in Philadelphia.
"Throughout human history we have the hero and we have heroines - literature is just rife with heroes, anti-heroes, heroism."
Asked to define what makes a hero, people share remarkably common preferences, experts have found.
The list includes courage, compassion, ambition, intelligence, humour, optimism and, perhaps surprisingly, being tall.
"A lot of the great heroes have the capacity of altruism, of generosity," said Farley. "They are giving people. They may give their life to others." Mandela, for his part, had emphasised willpower.
"A man who would not break down even under the most trying circumstances," is how he described a hero in his autobiography "Long Walk to Freedom."
According to the experts, real-life heroes tend to come in three categories.
There are those who commit their lives to struggling against societal wrongs; those who put their lives at risk to save a stranger, say from an oncoming train or a burning building; and "professional heroes" like firefighters or police officers.