  We propose using fuzzy axion dark matter to test the anthropic principle. A
very light axion can be directly detectable, at least by black hole
superradiance effects. The idea then is that gravitational and astrophysical
observations can discover a light axion in the regime where it must be all of
dark matter with abundance which must be set up by the anthropic principle, due
to excessive primordial misalignment induced by inflation. Yet it may turn out
that dark matter is something else instead of this axion. Since axion
misalignment must be induced by Brownian drift in (quasi)de Sitter space, this
could invalidate the anthropic prediction of the dark matter abundance.
