 Bostrom’s position owes nothing to skepticism, he is concerned solely with the question of whether virtual humans are empirically possible and, if so, how likely it is that we might be such beings. His argument, if sound, makes it look very doubtful that we can know a priori that we are not brains-in-a-vat, when BIVs are understood to be virtual humans in a  simulation.[6]  If Bostrom is correct, Putnam’s attempt to prove we cannot be BIVs must be flawed. However, the Simulation Argument is nothing if not controversial: it has provoked interest from cosmologists as well as philosophers [For discussion of the Simulation Hypothesis see Bostrom, 2005; Brueckner 2008; Chalmers 2010; Weatherson 2003]. 