 The central technical notion in Everett’s own formulation of the theory is a relative state: e.g. the electron is in a state of spin up relative to the corresponding read-out state of the apparatus and in a state of spin down relative to the other read-out state. But Everett is interested in the emergence of stable structures in the universal wavefunction in terms of relative states. His paradigm example is that of a hydrogen atom: put a proton and an electron in a box, both spread out over the entire volume. After a while, the proton and electron will have relaxed. The position of the proton will still be spread out over the entire box, but relative to each position state of the proton, the electron wil now be in the usual ground state of the hydrogen atom. According to Everett, this is what we mean by a stable atom forming. Everett thinks of classical systems (a cannonball!) along the same lines, and uses these arguments as justifying the assumption that classical systems exist, in particular ones that are complex enough to store (and perhaps act upon) records of measurement-like interactions they have had with their environments. Everett’s aim is to recover the usual predictions of quantum mechanics for the memory registers of such ‘servomechanisms’.[15][16] 