 Why accept SR3? Imagine a series of cases, beginning with a case involving a single atom and terminating with a case involving what would seem to be a paradigm stone, where each case differs from the preceding case only by the addition of a single atom. It seems highly implausible that there should be adjacent cases in any such series where there is a stone in one case but not in the other. Rejecting SR3 would look to commit one to just such a sharp cut-off.