  Are you, with your perceptions, memories and observational data, a Boltzmann
brain, namely a fleeting statistical fluctuation out of the thermal equilibrium
of the universe? Arguments are given in the literature claiming that this
bizarre hypothesis needs to be considered seriously, that all of our data about
the past is actually a mirage. We point to a difficulty in these arguments.
They are based on the dynamical laws and on statistical arguments, but they
disregard the fact that we infer the dynamical laws presupposing the
reliability of our data records about the past. Hence the reasoning in favor of
the Boltzmann brain hypothesis contradicts itself, relying on the reliability
of our data about the past to conclude that that data is wrong. More broadly,
it is based on incomplete evidence. Incomplete evidence notoriously leads to
false conclusions.
