 Grove spheres (Grove 1988) also suggest a natural method for static belief revision in plausibility models: if the agent is told by a completely trustworthy source that the actual world is among some nonempty subset \(S\subseteq \cc_a(w)\) of her informationally equivalent worlds, then she will restrict her attention to the worlds in S. The most plausible worlds in S will be the worlds she then considers to be most plausible overall, the next-most-plausible worlds in S will be the worlds she then considers to be next-most-plausible overall, and so on. That is, she will “reposition” her system of spheres around the set S. 