 The reason that it is possible to propose only an approximate prescription for the correspondence between the quantum state of the Universe and our experience is essentially the same reason for the claim of Bell 1990 that “ordinary quantum mechanics is just fine FAPP”. The concepts we use: “object”, “measurement”, etc. are not rigorously defined. Bell and many others were looking (until now in vain) for a “precise quantum mechanics”. Since it is not enough for a physical theory to be just fine FAPP, a quantum mechanics needs rigorous foundations. The MWI has rigorous foundations for (i), the “physics part” of the theory; only part (ii), corresponding to our experience, is approximate (just fine FAPP). But “just fine FAPP” means that the theory explains our experience for any possible experiment, and this is the goal of (ii). See Wallace 2002, 2010a, 2012 for more arguments why a FAPP definition of a world is enough.