 But if we do ask why we are what we are, we can explain more. Looking at the details of the physical world, the structure of the Hamiltonian, the value of the Planck constant, etc., one can understand why the sentient beings we know are of a particular type and why they have their particular concepts for describing their worlds. The main argument is that the locality of interactions yields the stability of worlds in which objects are well localized. The small value of the Planck constant allows macroscopic objects to be well localized for a long period of time. Worlds corresponding to localized quantum states \(\ket{\Psi_{\world\ i}}\) do not split for a long enough time such that sentient beings can perceive the locations of macroscopic objects. By contrast, a “world” obtained in another decomposition, e.g., the “world +” which is characterized by the relative phase of a superposition of states of macroscopic objects being in macroscopically distinguishable states \(A\) and \(B\), \(1/\sqrt{2}\,(\ket{\Psi_A} + \ket{\Psi_B})\ket{\Phi},\) splits immediately, during a period of time which is much smaller than the perception time of any feasible sentient being, into two worlds: the new “world+” and the “world\(-\)”: \(1/\sqrt{2}\,(\ket{\Psi_A}-\ket{\Psi_B})\ket{\Phi'}.\) This is the phenomenon of  decoherence  which has attracted enormous attention in recent years, e.g., Joos et al. 2003, Zurek 2003, Schlosshauer 2007, Wallace 2012, Riedel 2017, Schlosshauer 2019, Boge 2019, Saunders forthcoming-a also in the “decoherent histories” framework of Gell-Mann and Hartle 1990, see Saunders 1995 and Riedel et al.2016.