You decide to perform an experiment: you’ll wait fifteen seconds. If your experience dissolves into chaos, Boltzmann brains made a correct prediction. If it doesn’t, they made an incorrect prediction… After performing the experiment, you get the non-Boltzmann brain result, and this experiment is very well-replicated.
You could be a Boltzmann brain who believes that it was confused fifteen seconds ago and performed the experiment, when in fact it hasn’t.
You could be a Boltzmann brain who believes that it was confused fifteen seconds ago and performed the experiment, when in fact it hasn’t.