One way to see the difference between my representational states and the Boltzmann brains' is to think counterfactually. If Barack Obama had lost the election in 2008, my current brain state would have been different in (at least partially) predictable ways. I would no longer have the belief that he was President, for instance. The Boltzmann brain's brain states don't possess this counterfactual dependency. Doesn't this suggest an epistemic difference between me and the Boltzmann brain?