In Chapter i, I assume that the unknown world outside our diving bell occupies the same space as the physical one, and is superposed on it. We are in a sense immersed in it, just as we are immersed in physical space; I take the two worlds as very weakly coupled. In this chapter, I consider what limitations may be placed on the unknown world by that superimposition. My suggestions are, of course, scientific guesswork, but they may at least provide a framework for thinking about that world.