"Behold! human beings living in a underground cave, which has a mouth open towards the light and reaching all along the cave; here they have been from their childhood, and have their legs and necks chained so that they cannot move, and can only see before them, being prevented by the chains from turning round their heads. Above and behind them a fire is blazing at a distance, and between the fire and the prisoners there is a raised way; and you will see, if you look, a low wall built along the way, like the screen which marionette players have in front of them, over which they show the puppets.
And now look again, and see what will naturally follow if the prisoners are released and disabused of their error. At first, when any of them is liberated and compelled suddenly to stand up and turn his neck round and walk and look towards the light, he will suffer sharp pains; the glare will distress him, and he will be unable to see the realities of which in his former state he had seen the shadows; and then conceive some one saying to him, that what he saw before was an illusion, but that now, when he is approaching nearer to being and his eye is turned towards more real existence, he has a clearer vision, -what will be his reply? And you may further imagine that his instructor is pointing to the objects as they pass and requiring him to name them, -will he not be perplexed? Will he not fancy that the shadows which he formerly saw are truer than the objects which are now shown to him?"
Plato's Republic, book vii, 514a-c to 521a-e
[Plato's allegory about consciousness underpins Western philosophy. It also introduces a fundamental concept used by Christian theology to describe spiritual enlightenment.]
"Located deep in the Luray Caverns in Virginia's Shenandoah Valley is the Great Stalacpipe Organ, the worlds largest musical instrument.
Stalactites covering 3 1/2 acres of the surrounding caverns produce tones of symphonic quality when electronically tapped by rubber-tipped mallets.
This most unique, one-of-a-kind instrument was invented in 1954 by Mr. LeIand W. Sprinkle of Springfield, Virginia, a mathematician and electronic scientist at the Pentagon."
Oliver Grau (2003 Virtual Art)
Millstones - an incomplete history: