The thought is hallucinatory. Do we live in a virtual world created by a highly technically advanced civilization? According to some philosophers, this is more likely than we live in a real world. What are the chances that we live in a Matrix-like world without realizing it?
I think therefore I am
This famous saying of the French philosopher René Descartes from the seventeenth century is the only basis we have to objectively determine that we exist. Whatever we are: a gray jelly in our skull, an immortal soul, part of a computer program somewhere in an unknown universe - that we exist in one form or another is certain. Although that existence may be an illusion, as Buddha stated. The problem is that you cannot apply this technique to others. You can't read the thoughts of others - although body language and psychological insight can get you quite far.
Do we live in a computer world?
We now know that computers can become powerful enough to create virtual worlds. Anyone who has ever played a graphically realistic computer game has, as it were, plunged into a world within our world. Computers are still rapidly increasing in capacity and computing power. In the medium to distant future, the 'original' universe will be filled with countless virtual civilizations. Chances are, these virtual worlds will contain sentient beings like you and me. Remarkably, Buddhism and Hinduism state that we live in such a virtual world.
According to Oxford University philosopher Nick Bostrom, who first used this argument, it is quite possible that our reality is in fact a simulation run by beings from a more advanced civilization. It is virtually impossible for us to find out whether we are living in a simulation. Only if the system administrator of the virtual world - let's call him God - decides to make his existence known, for example by floating a large text before our eyes with the text: you live in a computer simulation, according to Bostrom we would find out that we live in a virtual world. Another option is that we are uploaded by the operators to a body in their reality.
While we probably won't get to see any evidence - that would ruin the simulation after all - we may be able to find some hints to give us clues. Inconsistencies, disruptions in reality and the like. When a bunch of third-rate programmers finish a rush job, you inevitably see the signs of it.
Economist Robin Hanson thinks that chance is relatively small. As soon as evidence of this emerges, the system administrators will reset the simulation and erase the traces. Otherwise the game is over - although I can imagine that the game will become much more interesting ...
Hanson thinks there are many more small-scale simulations than large-scale simulations. He thinks he is the only person living in this simulation. All other people are dolls, zombies as it were. I believed this at one point when I was nine. However, it is extremely inefficient to set up a complex world simulation just for one test subject - the argument for me to put this thought aside. It is then much smarter to use many more test subjects. It is not that much more difficult - unless your world of experience is as limited as that of the average economist, of course.
Burglary to the brain
Now we are able to sort of read people's minds with brain electrodes and things like that. But unfortunately: we do not know what experience someone undergoes when a certain brain wave is stimulated. Although in theory you could scan areas of the brain so that you know which areas of the brain are involved in processing the brain wave. If it is the pleasure center in the pituitary gland, the associations are clearly different from when the center that arouses fear and pain is stimulated. Not very subtle, but that gives you a rough impression. Our increased knowledge of the brain also implies that we ourselves may be zombies. But still. Obviously our thoughts will be traced back to some physical "bedrock". That doesn't make our thoughts and feelings any less real. Whatever the source of our complexity, we are complex and that complexity is real. We think, so we exist.