Here's the punchline: to an inhabitant living in one of these simulated universes, there would be no way to determine whether that universe is real (as in not simulated). If there ever is a bug in the program, and someone discovers that they are indeed living in a simulation, then the simulators can simply erase that person's memory, or fix the problem and rewind the program. There is no way to know for sure whether our universe is simulated or not, but we can reason about the probability that we are: if there is one real universe, whose inhabitants simulate a billion, or a trillion, virtual universes, the probability that we are living in the one real universe is vanishingly small. If we accept every step of the argument presented above, then we must conclude that we are almost certainly living in a computer simulation.
Bostrom then presents a trilemma:
(1) It is highly unlikely that we will ever become a posthuman civilization with such enormous computing power.
(2) Such a posthuman civilization will have no interest in running large-scale ancestor simulations.If (1) and (2) are false then:
(3) We are almost certainly living in a simulated universe.The simulation argument is an interesting one to wrangle with. Can you find any flaws in the logic? Obviously, if one denies the premise that minds can be simulated on a computer, then the rest of the argument is moot. But if one accepts that premise, the rest sounds pretty reasonable. I think the simulation argument has widespread appeal because it couches what is essentially a creation myth in the language that a scientifically-minded person would accept. To demonstrate this, I will recast the simulation argument in a slightly different way:
There exists a supernatural being, called God. God himself inhabits a universe, but He has the ability to create as many new universes as He wishes. What is the probability that we are living in the original universe, God's universe? If there are countless universes created by God, then it is almost certain that we are God's creations.Now you may find this argument rather specious, even if you accepted Bostrom's simulation argument. The difference between the two is that the God argument just postulates a "supernatural being" who may possess any number of characteristics (depending on which religion you follow); on the other hand, the simulation argument says that the Creator is just an evolved version of us, humanity. An atheist does not believe in God because there is no evidence for his existence. But if we ourselves become creators of new universes, then that is compelling empirical evidence that the process of Creation by Computer is not only possible, but an extremely likely explanation for the existence of our universe.
People have speculated about what it might mean to live in a simulated universe. The answers they've arrived at are, in my opinion, a bit silly. Be as interesting as possible, they say, so that the programmers don't end our simulation out of boredom. Don't care too much about humanity and the distant future (a future that might never be simulated), and live for today.
Alternatively, Bostrom himself imagines that perhaps the creators are judging the morality of our actions. We must be good, because they might punish us for bad behavior once the simulation ends.
Yet another possibility is that the creators are not simulating the entire universe, but only your mind. Everyone else is just a figment of your imagination with enough believability to convince you that they are real people, when really they are merely a collection of perceptions in your brain.
But why bother even simulating a whole person? You might be nothing more than a snapshot of a psychological state, at a certain point in time. You believe you have a past, and a future, but you perceive the past through your memories, and you apprehend the future through your expectations. Both memories and expectations are just ways your current perceptions could be coded onto a flash drive. In other words, there is no passage of time, just the illusion of it.
Are you a hedonist, a Christian, a solipsist, or a Buddhist? If you haven't decided yet, then Bostrom's simulation argument can't help you. We might yet become gods, but that doesn't mean we know what God expects of us.