My colleague Roger Penrose once said that there are at least three worlds and three mysteries. One is the physical world. You know, this is the world where we exist. There are chairs, tables, there are stars, there are galaxies, and so on. Then there is a second world, which is the world of our consciousness, if you like. You know, a mental world, a world where — this is where we love, where we hate, you know, and so on. All our thoughts are there and so on. And then there is the third world, which is this world of mathematical forms. This is the world where all of mathematics is there. You know, the theorem of Pythagoras and so on and so forth, all this imaginary numbers and all that. So these are the three worlds. And now come these three mysteries. One mystery is that somehow, out of the physical world, our world of consciousness has emerged.