Figure 26: Existence in a nutshell. A schematic depiction of the set of all that can in principle exist. A distinction is made between what actually exists and what could exist but doesn’t. Included within the former set is a smaller subset, consisting of all that can in principle be observed. Left out of this subset are other things that exist but are unobservable (for example, universes that do not permit life). Anthropic reasoning may be applied to boundary A,
