 Second, contrary to what DeWitt, Graham, and others have supposed, Everett was not committed to causally isolated worlds. In contrast, as we have seen, Everett held that it is always in principle possible for branches to interact. More specifically, he argued that “no matter what the state of [Wigner’s Friend] is, there is in principle a complete set of commuting operators for which it is an eigenstate, so that, at least, the determination of these quantities will not affect the state nor in any way,” he denied that there are fundamental restrictions about the “knowability of any state functions,” and he believed that the sense in which all branches of the global state are equally actual is given by the ever-present possibility of interaction between branches. So while one clearly can describe situations where there is no post-measurement interference between the branches representing incompatible measurement records, one can also describe interactions where there is, and for Everett there was no special physical distinction to be made between the two cases. 