Summary:
• The idea that our world might be a computer simulation became popular in the twentieth century after computer games were invented, especially games that let players create imaginary worlds. However, most scientists do not treat this idea as a scientific theory because it cannot be tested scientifically.
• If this world were a simulation, you would not know it unless the simulation’s operator decided to tell you—and even then, you could not be certain that you were being told the truth.
• In a genuine computer simulation, the characters do not need actual private thoughts. The computer needs only to make them appear to think and then behave plausibly, as a show for the operator who is watching. The only real thoughts belong to the operator. The characters would be like actors following a script, presenting the appearance of thinking but not really thinking.
• The fact that you have private thoughts—an inner world which a computer would not need to create—is a strong clue that you are not simply a character in somebody else’s computer simulation. As the philosopher René Descartes said, “I think, therefore I am.” Your ability to think is proof that you genuinely exist, regardless of whether the world around you is real or simulated.
If this world is an illusion, is it a computer simulation? Probably not.
The first computer games were invented in the late twentieth century. Some of those games offered players the opportunity to create imaginary worlds which the computer would depict. People began to wonder, if a computer can simulate a world, might the world we live in be a simulation depicted by a super-computer? This idea became a theme in several science fiction stories. However, most scientists do not treat this idea as a scientific theory because it cannot be tested. If this world is a computer simulation, then you would never know it unless the operator of the simulation decided to tell you. (If the operator did tell you, would you believe it? How could you be sure?)
Nevertheless, there are strong clues that this world is not a computer simulation. If it is, then the simulation has diverged from the original purpose of a computer game. That purpose is to give the operator an experience. The thoughts of the operator are the only thoughts that actually exist. The characters in the game may appear to have thoughts, but they are like actors in a play: they may look like people and say that they have thoughts, but their behavior is only a portrayal, a depiction, an illusion. They do not really have thoughts. They are characters portrayed according to a script written by the author of the play. The only thoughts the characters have are thoughts created by the author, who imagines and decides what the characters think. The goal of the author is to make the experience of watching the characters interesting. The game would perform well enough if the characters only appear to think, but the computer does not require them to actually think within the privacy of their own minds. What the computer depicts is good enough because the operator is watching the entire depiction, an image, a game.
If you wonder if you might be living in a computer simulation, then why, at this moment, is your mind thinking about anything at all? Are you supposed to be experiencing the simulation? Experiencing it is the only reason why you would need to actually think. Otherwise, the computer could simulate your behavior without you having any actual thoughts. Within the privacy of your mind, your thoughts are an inner world. A computer simulation has no need for that inner world, not unless you are meant to experience the simulation. Thinking is experiencing. And if you are thinking, that means you do exist, regardless of whether your world is real or a computer simulation. In the words of the French philosopher René Descartes, “Cogito, ergo sum.” I think, therefore I am.