This is the idea of the ‘Multiverse’. It is often, though not always, associated with the idea of ‘anthropic cosmology’, which suggests that we see around us a Universe just right for life because there is a multitude of universes with different physical laws, and life forms like us can only exist in universes like ours. The others are sterile, so there is nobody there to notice what their strange laws of physics are.
Apparently this whole book takes the multiverse for granted--specifically the Everett Multiverse. The multiverse could exist, it would be convenient if it did, and therefore it must.
