William James, father of American psychology, tells of meeting an old lady who told him the Earth rested on the back of a huge turtle.
"But, my dear lady," Professor James asked, as politely as possible, "what holds up the turtle?"
"Ah," she said, "that's easy. He is standing on the back of another turtle."
"Oh, I see," said Professor James, still being polite. "But would you be so good as to tell me what holds up the second turtle?"
"It's no use, Professor," said the old lady, realizing he was trying to lead her into a logical trap. "It's turtles-turtles-turtles, all the way!"

Don't be too quick to laugh at this little old lady. All human minds work on fundamentally similar principles. Her universe was a little bit weirder than most but it was built up on the same mental principles as every other universe people have believed in.

As Dr. Leonard Orr has noted, the human mind behaves as if it were divided into two parts, the Thinker and the Prover.

The Thinker can think about virtually anything. History shows that it can think the earth is suspended on the backs of infinite turtles or that the Earth is hollow, or that the Earth is floating in space; comparative religion and philosophy show that the Thinker can regard itself as mortal, as immortal, as both mortal and immortal (the reincarnation model) or even as non-existent (Buddhism). It can think itself into living in a Christian universe, a Marxist universe, a scientific-relativistic universe, or a Nazi universe—among many possibilities.

As psychiatrists and psychologists have often observed (much to the chagrin of their medical colleagues), the Thinker can think itself sick, and can even think itself well again.

The Prover is a much simpler mechanism. It operates on one law only: Whatever the Thinker thinks, the Prover proves.
<...>

~Prometheus Rising
Robert Anton Wilson