Here is something of a philosophical question for you: "What is wisdom?"
This is what some well-known figures from around the world think.
The voices there of Billy Connolly, Judi Dench, Chinua Achebe, Ravi Shankkar, Desmond Tutu and Jane Goodall - all with their reflections on what wisdom is.
They were all photographed and interviewed by American photographer, Andrew Zuckerman.
He went around the world in search of wisdom, meeting a total of 50 well-known international figures, all aged 65 or over.
Their words of wisdom, and their photos, are collated in a book he's just brought out, called simply: Wisdom.
George Arney met up with him recently in London and he explained why he had embarked on this project.
First broadcast 2 January 2009