The multiverse hypothesis is that what we used to see as the Universe (which is supposed to be all that there is) may be part of something larger, that includes other universes like, or unlike our own. This is not a hypothesis that was proposed to conveniently solve the Anthropic paradox (we don’t know why the Universe can support life at all whereas it could be a lot more hostile and sterile than it already is, as far as we can tell). It does solve that problem, but wasn’t proposed for that reason. It emerges, actually, in four different forms, as a necessary consequence of scientific theories for which we have very good evidence. Some levels of multiverse are more controversial than others, of course, but in this post, I want to bring forward another argument in favor of multiverses, based on symmetry.