In fact, if we don't believe we are simulations, concludes Bostrom, then "we are not entitled to believe that we will have descendants who will run lots of such simulations of their forebears." If you accept one premise (that you'll have powerful super-computing descendants), you have to accept the other (you are simulation). [...]
Simulating the whole universe, including all the details "down to the quantum level" requires more computing oomph, to the point that it may be "unfeasible," thinks Bostrom. But that may not really be necessary as all the future humans or post-humans would need to do is to simulate the human experience of the universe. They'd just need to make sure the simulated minds don't pick up on anything that doesn't look consistent or "irregularities". You wouldn't have to recreate things the human mind wouldn't ordinarily notice, like things happening at the microscopic level. [...]
A fascinating outcome of all this speculation is that we have no way of knowing what the true reality of existence really is. Our minds are likely accessing just a small fraction of the "totality of physical existence." What we think we are may be run on virtual machines that are run on other virtual machines - it's like a nesting doll of simulations, making it nearly impossible for us to see beyond to the true nature of things. Even the posthumans simulating us could be themselves simulated. As such, there could be many levels of reality, concludes Bostrom. The future us might likely never know if they are at the "fundamental" or "basement" level. [...]
What are other implications of these lines of reasoning? Ok, let's assume we are living in a simulation – now what? Bostrom doesn't think our behavior should be affected much, even with such heavy knowledge, especially as we don't know the true motivations of future humans behind creating the simulated minds. They might have entirely different value systems.