Watch . . . This is space. It's sometimes called the final frontier. (Except that of course you can't have a final frontier, because there'd be nothing for it to be a frontier to, but as frontiers go, it's pretty penultimate . . .) And against the wash of stars a nebula hangs, vast and black, one red giant gleaming like the madness of gods . . . And then the gleam is seen as the glint in a giant eye and it is eclipsed by the blink of an eyelid and the darkness moves a flipper and Great A'Tuin, star turtle, swims onward through the void. On its back, four giant elephants. On their shoulders, rimmed with water, glittering under its tiny orbiting sunlet, spinning majestically around the mountains at its frozen Hub, lies the Discworld, world and mirror of worlds. Nearly unreal. Reality is not digital, an on-off state, but analog. Something gradual. In other words, reality is a quality that things possess in the same way that they possess, say, weight. Some people are more real than others, for example. It has been estimated that there are only about five hundred real people on any given planet, which is why they keep unexpectedly running into one another all the time. The Discworld is as unreal as it is possible to be