Anyone who has seen 'The Matrix' has spent some time worrying that they're stuck inside a computer simulation and aren't really experiencing the 'real world'. It's easy to brush off at first since it seems like silly science fiction.
It doesn't seem like there's any good reason to doubt that we're living in the real world, so why bother trying to prove that we are?
Occam's Razor suggests that if you have to choose between two explanations, the simpler one is most likely true. The simplest explanation of our experiences is that when we see a tree, it's because the tree is actually there!
However, there are good reasons for not being so quick to dismiss the possibility that you're actually a computer simulation. Nick Bostrom, Oxford Philosopher and 'transhumanist' has written a really interesting paper that will make you revisit concerns you brushed off so easily first time around!
The Simulation Argument
In its basic form, the argument goes as follows:
In the future, it is possible that humans could develop computers powerful enough to run a simulation of the history of their civilisation. In other words, at some point, our computers will be so powerful that we could create a complete simulation of 21st Century Earth. It could be 100 years from now or 100,000 years from now. All we need to agree on is that if we gave it enough time, we would eventually build a computer with the power required.
So, we're at some point in the future and we've got a super computer that can simulate the entirety of history and human civilization up to this point. The simulations would be so fine grained and detailed that the simulated people would have conscious experiences just as we do.
Look at how the robots in 'The Matrix' produced a simulation of 20th Century Earth. From intelligent programs to the human minds 'trapped' in the matrix - they all had conscious experiences that were qualitatively indistinguishable from the 'real world' experiences. So in this universe, there are trillions of conscious human experiences that take place in a computer simulation. 'Human-like experiences' are not restricted to real humans in the real world.
This has big implications for our future super computer.
If these future humans decided to run a simulation (or multiple simulations) of their history, then the total number of 'human-like experiences' will be made up of all the simulated human experiences, plus all of the real world, actual human experiences:
As displayed in the image, the vast majority of the total human like experiences will be simulated ones. 'Real world' experiences will be a tiny tiny fraction of the total.
So given all of this and the experiences you're having right now: Is it more likely that the experiences you're having are simulated or real?
One of the following must be true:
A) Human kind will never reach this point in their development. We will become extinct before attaining this level of computing power.
B) Human kind will reach this level of computing power, but will never run a simulation of its history. This would mean there are not trillions of simulated human experiences.
C) It is almost certainly the case that a person experiencing the sort of things that we experience is living in a simulation.
What does this mean?
So, which option is most likely? If you'd like to think that you're not a simulation, then it must be because either human kind will one day be wiped out of existence (not a very comforting idea), or because they will decide not to simulate human history (surely they would if they could?).
On the other hand, you might decide that being a simulation isn't so bad. There's no obvious way to tell for sure what the truth is, so perhaps we should just get on with things!
If you'd like to read more, check out: Nick Bostrom's original paper.