 Many physicists nowadays believe that a specific version of the multiverse hypothesis is indeed suggested by contemporary developments in fundamental physics, notably by the combination of inflationary cosmology and string theory, both of which have been introduced in  Section 2.3.  According to many advocates of inflationary cosmology, the process of inflation results in causally isolated space-time regions, so-called “island universes”. This process is in general “eternal” in that the formation of island universes never ends. As a result, it leads to the production of a vast (and, according to most models, infinite) “multiverse” of island universes (Guth 2000).