It happened once upon a time that the Sun and a Cave had a conversation. It was a philosophical sort of talk, and they discovered that for each one of them, there were certain matters that were incomprehensible.

The Cave, whose inner recesses extended far underground through shadowy, dripping chambers to the roots of a mighty mountain, declared that the words ‘bright’ and ‘clear’ had always seemed to be meaningless concepts. The Sun, blazing in the sky, said that the words ‘dark’ and damp’ had likewise been no more that vague and puzzling ideas.

“We should trade places, ‘ said one of them, and so the Cave first came up into the realm of the Sun. ‘Ahh,’ said the Cave. ‘Now I DO understand. How wonderful is brightness and clearness! Thank you!’

Then it was the turn of the Sun to descend into the underground world of the Cave. ‘But–’ said the Sun, looking about, ‘I see no difference!’