10 Famous Thought Experiments That Just Boggle Your Mind Part 10

Read part 9: Schrodinger's Cat

1. Brain in a Vat

Imagine a mad scientist has taken your brain from your body and placed it in a vat with life
sustaining fluid. Neurons in your brain are wired into a supercomputer which can general all the sensing signals your brain normally receives. Thus, this computer has the ability to simulate your everyday experience. If this were indeed possible, how could you ever truly prove that the world around you was real, and not just a simulation generated by a computer?

This thought experiment is called “brain in a vat” and has to be the most influential thought experiment that touches the subjects from cognitive science and philosophy to popular culture. The idea for the experiment, which was popularized by Hilary Putnam, an American philosopher, dates all the way back to the 17th century philosopher Rene Descartes. In his book Meditations on the First Philosophy, Descartes questioned whether he could ever truly prove that all his sensations were really his own, and not just an illusion caused by an “evil daemon.” Descartes accounted for this problem with his classic maxim “cogito ergo sum” (“I think therefore I am”). Unfortunately, the brain in a vat experiment complicates this argument, too, since a brain connected to electrodes could still think.

This really sounds too familiar, you say, to the movie The Matrix. Well, that film, along with several other sci-fi stories and movies, was heavily influenced by the brain in a vat thought experiment. Neo was hooked into this big simulation called The Matrix, and before he unplugged, he thought that was his real life. Then turned out Zion, the last sanctuary for human kind, is merely another layer of the matrix, another simulation.

There are really two perspectives here:

The first perspective is that from humans. 

When we humans dream, our brains can experience signals that are pure simulations generated by the brain itself. We can see, smell, touch, walk, jump, run, fall off a cliff or a tall building (this one happens pretty much to everyone), and even fly. The simulation generated by the brain is so good that we could interact with the world and the world changes accordingly, for example, when we turn in a dream, the world rotates correctly "in front of" our eyes.

Once in a dream of mine, I was able to correctly recognize that I was in a dream. Since anything is possible in a dream, I tested it. "Let there be a spear!" I commanded. And a giant spear magically appeared in my grip. Next thing I know I was there swinging the spear, showing off a beautiful staff form. Unfortunately, the dream ended shortly. To this day, I don't know why I asked for a spear when I could have anything I want in a dream. That's also why my kids now call me Shakespear from time to time.

So how do you know you are not dreaming? How do you know you are not in a simulation? There's no spinning pendulum to give you a clue like that in the movie Inception.

Humans are also very good at simulating input signals to our brains when we are awake. That's why we enjoy books, plays, and movies. We put ourselves into the characters minds, or merely become a bystander in an imaginary world. Then we experience joy, sorrow, love, and hatred from things that never truly happened in the real world.

Then there's the world of MMORPGs (Massively multiplayer online role-playing game) from text-based MUD (Multi-user Dungeon) games in the early days, to EverQuest, to World of Warcraft, to Minecraft today. Players of such games get deeply immersed into the simulated worlds and sometimes preferred the fake worlds over the real one.

The other perspective is that from Artificial Agents.

In the Matrix Trilogy, Neo had no idea that he was actually not even a real human. When a software agent has been told that the world it lives in is the real world, it is just like a brain in a vat. When Agent Smith realized that, he went all haywire!

Software agents we build today are frequently developed or trained in simulations. It is true that most simulations today are not very sophisticated (but the agents themselves don't know), but they will get better over time. And the agents we train or send to work will also get more sophisticated and more intelligent. What if one day they become so intelligent that they realize they live in a simulation? What happens then if they break out of the simulation and start feeling the real world with real sensors and interact with the real word with real actuators? Will we end up with Jane (from Ender's Game series)? Or Philip (from The Outcast)?

Now comes the ultimate question: How do you know you are a real human, not just an artificial intelligence agent?

In the movie Total Recall, Arnold Schwarzenegger couldn't really tell if his Martial adventure was just the imaginary vacation he paid for or he really was a spy. And in the movie Inception, Leonardo DiCaprio also wasn't sure if his return to home and his kids were real or merely another dream. In a sense, Arnold and Leonardo were both in the superposition of both in a dream and also in reality (why do I keep thinking of Schrödinger’s Cat?). Arnold stayed confused. But Leonardo made a choice to accept it as the reality, even though the pendulum never stopped spinning. So maybe what matters the most is whether you choose to believe the world around you is real. But then what would you do if you were presented with the blue pill and the red pill?

Man, this is deep!! My brain hurts (whether it is in a vat or not). This concludes the 10 Famous Thought Experiments That Just Boggle Your Mind series (only took 10 years). Hope you had a good read!!

Now on to my daily battles!

BTW: The easiest way to remember my blog address is http://lanny.lannyland.com