  Valid ideas that physical reality is vastly larger than human perception of
it, and that the perceived part may not be representative of the whole, exist
on many levels and have a long history. After a brief general inventory of
those ideas and their implications, I consider the cosmological "multiverse"
much discussed in recent scientific literature. I review its theoretical and
(broadly) empirical motivations, and its disruptive implications for the
traditional program of fundamental physics. I discuss the inflationary axion
cosmology, which provides an example where firmly rooted, plausible ideas from
microphysics lead to a well-characterized "mini-multiverse" scenario, with
testable phenomenological consequences.
