He says that imagine if society was living in a cave. A dark cave chained to the floor and all they had was a little fire that cast shadows on the wall. And that they would live there for centuries looking at these shadows and they would develop great theories and wisdom and intelligence and knowledge about those shadows. And then one day somebody would figure out I can crawl out of the cave. They crawl out of the cave and there would be the glorious sun shining upon life itself. And this person would be amazed. They would see things they never thought ever existed.