The objection is totally relevant because you cannot calculate probabilities if you don't know the number of real universes, the probability of life arising from non-life, etc. I would argue, using that line of reasoning that it is more likely that we would be a dream of a sentient entity rather than a simulation of one if his probabilistic assumptions are taken as probable.
Dreams only last a few hours, so that's not really a possibility. If you are proposing we are the "dreams" of a sentient and extremely advanced machine, then that is hardly different from saying that we are just simulated.
And I'm pretty sure the numbers you mentioned--like the number of real universes, the probability of life arising from non-life--really don't come into it at all. Skimming over the paper, none of that stuff seems to come up at all. Again, this isn't about universes inside universes (the news article phrased the argument poorly).
Im not talking about universes within universes. Let's take our own universe as an example, and using probability as we know it in our own as holding in whatever 'real' universe(s) that may or may not simulate itself or some subset of itself. If sentient beings evolve (taking Bostroms postulate of that probability as reasonably high) and assuming they 'dream' if they are anything like us, as he does, and since we have (yet) to develop a technology that can simulate a universe as complex as ours, it's far more probable that sentients evolve and dream universes than evolve and simulate us. Even in our own "existence" (whatever that means) you have to agree that there have been far more dreams than games played. This follows probabilistically; not all people play games but almost every human that has ever lived has dreamed. Therefore it is far more probable that we are a dream, or passing thought, for that matter, than an intended simulation. Hinduism win.
