Greg Bear in the 1987 novel “Eon” describes a virtual “afterlife“ where both the world and the people in it are simulated. He also describes a theory where you

Greg Bear in the 1987 novel “Eon” describes a virtual “afterlife“ where both the world and the people in it are simulated. He also describes a theory where you could design a system in such a way that the simulated people wouldn’t be able to tell the true state of the world. And (spoiler alert) he also introduces an Alien race that has discovered algorithms that let them subvert the simulation.