  Recall the informal picture that we began with: a world is, so to  say, the “limit” of a series of increasingly more  inclusive situations. Fleshed out philosophical accounts of this  informal idea generally spring from rather different intuitions about what one takes the “situations” in the informal picture  to be. A particularly powerful intuition is that situations are  simply structured collections of physical objects: the  immediate situation of our initial example above, for instance, consists  of, among other things, the objects in Anne's office  — notably Anne herself, her desk and her computer, with her  seated at the former and typing on the latter — and at least  some of the things in the next room — notably, her husband and  the phone he is talking on. On this view, for one situation s  to include another r is simply for r to be a (perhaps  rather complex and distributed) physical part of s. The actual world, then, as the limit of a series of increasingly more inclusive  situations in this sense, is simply the entire physical universe: all the things that are some spatiotemporal distance from the objects in  some arbitrary initial situation, structured as they in fact are; and other possible worlds are things of exactly the same sort. Call this  the concretist intuition, as possible worlds are understood to be concrete physical situations of a special sort. 