Reality + Virtual Worlds and the Problems of Philosophy by David J. Chalmers

We create simulations in this reality, computer simulations made up of 0s and 1s. Now imagine some entity at a higher level, which simulates us using atoms, quarks, and whatever. Atoms, quarks as well as 0s and 1s are building blocks that create different kinds of realities. They are different, but they are realities non the less. So, even if we live in a simulation, this is still our reality, not an illusion. In a few decades/centuries, technology could be so advanced to make perfect digital copies of our brains. And if the brain copies are so perfect, they could potentially be conscious. We could build simulations inhabited by conscious Sims (simulated people). Since they are conscious, they posses moral status. It follows then that the creation of simulations would need ethical considerations, to not violate Sims's rights. There is so much on this book, a good chunk of which goes beyond me, I can not summarise, so I included a synopsis below.