_Turtles All the Way Down  

Stephen Hawking in A Brief History Of Time starts with the anecdote.
A well-known scientist (some say it was Bertrand Russell) once gave a
public lecture on astronomy. He described how the earth orbits around the
sun and how the sun, in turn, orbits around the centre of a vast collection
of stars called our galaxy. 

At the end of the lecture, a little old lady at
the back of the room got up and said: "What you have told us is rubbish.
The world is really a flat plate supported on the back of a giant
tortoise." 

The scientist gave a superior smile before replying, "What is
the tortoise standing on?" 

"You're very clever, young man, very clever,"
said the old lady. "But it's turtles all the way down."

Well, it isn't turtles all the way down. 

In a phrase, "A  people acquire and retain well being in proportion to the knowledge they possess – and the use to which they put it."