 In the final long version of his thesis, Everett further explained in a footnote that “[t]he word homomorphism would be technically more correct, since there may not be a one-one correspondence between the model and the external world” (1956, 169). The map is a homomorphism because (1) there may be elements of the theory that do not directly correspond to experience and because (2) a particular theory may not seek to explain all of experience. It is case (1) that is particularly important here: Everett considered the surplus experiential structure represented in the various branches of the absolute state to be explanatorily harmless.