Famous Thought Experiments (Part 2)

brain in a vat

In the previous article - Famous Thought Experiments, we took a look at the thought experiments of the Trolley Problem, the Ship of Theseus and Schrödinger’s Cat. Let’s explore some other thought experiments in this article. 

Brain in a Vat

Imagine that you are actually just a brain connected to a computer, which is able to perfectly simulate your experience of the outside world. This world you are experiencing is, in fact, just a creation of the computer. Now, how can you prove that you are not really just a brain connected to a computer? 

If you cannot be sure that you are not a brain in a vat, then how do you know that your beliefs of the outside world are real? 

This thought experiment essentially asks, how do we know that what we know is real? How do we know that this world we are experiencing is real? What if, all this while, our brains are really existing in a vat that simply simulates this world and all our sensations, but none of it is real? What if this world that we know is just a simulation, but it feels so real to us, so we would never know that it was really a virtual reality until we wake up? 

Is this starting to sound like the Matrix? Well, you’re right. The concept for the Matrix was based on this thought experiment which was popularized by Hilary Putnam. However, the idea behind the Brain in a Vat thought experiment really dates back to the philosopher René Descartes in the 17th century, who came up with the famous philosophical statement, “cogito, ergo sum” – “I think, therefore I am”. Descartes questioned whether he could truly prove that all his experiences were really his own and not just illusions. As such, he coined his popular maxim, believing that since he was able to think and had these doubts about his existence, therefore his thinking identity should be a reality. 

However, this does not really solve the brain in a vat problem. The scenario makes some assumptions, but we assume that even if we are really brains in a vat, we are still able to think – but that does not prove if our world is real or just an illusion. 

Many objections have been raised regarding the premises of the brain in a vat, but to this day nobody really has a rebuttal for the problem. Similar concepts have also been popularized in films and novels such as Inception, Existenz, and the Truman Show. 

Ticking Time Bomb

There is a nuclear bomb hidden somewhere in a city and set to detonate soon. You have in custody a criminal who is the only person with the knowledge of where the bomb is planted. Will you resort to torturing this criminal to get the information and save everyone’s lives? 

Some renditions of the Ticking Time Bomb take this problem further, stating that you know the criminal will not respond to any form of torture done to their body. Will you resort to torturing the criminal’s innocent family to get the information instead? 

This thought experiment is a discussion of ethics, similar to the Trolley Problem. While torturing someone is against most moral codes of conduct, doing nothing and allowing the bomb to kill millions of innocent people may also be just as questionable. The Ticking Time Bomb is commonly used as a counter argument against the belief that torture is inherently wrong under any circumstances. Although torture is regarded as widely illegal and many countries have laws against torture, this thought experiment is an example that under certain circumstances, some laws may potentially be set aside. 

Some oppositions tend to question the premises and assumptions of this thought experiment, such as whether one can be sure if the criminal has useful information and if the criminal will respond to the torture (i.e. the effectiveness of torture). While we can make assumptions in the scenario, we are hardly certain about such details in real life, which may defeat the purpose of debating about the thought experiment in the first place. 

This scenario was first suggested by the philosopher Jeremy Bentham in an essay dated 1804. Since the past century, the problem has been widely popularized through recent political debates as well as in the entertainment sector, in action movies and television shows. 

Mary’s Room

One version of the thought experiment goes as follows: in a black-and-white world, Mary is a brilliant neuroscientist who specializes in studying the color blue. She learns about the wavelength of visible light and the specific frequencies that make up all the different shades of blue. In terms of physical knowledge about the color blue, she knows all there is to know about it, such as how light enters the retina and the brain processes that information, which then causes the mind to interpret that color as blue. However, remember that Mary is studying all of this in a black-and-white world and has never seen the color blue herself. Now, suppose that one day Mary is transported to a world with color and she sees a blue wall for the first time. Firstly, will she recognize that the wall is blue? Secondly, once someone confirms to Mary that yes, that wall is indeed blue, will Mary learn anything new from actually seeing blue for the first time? 

This thought experiment was first proposed by Frank Jackson in 1982, with the aim to establish whether there are non-physical properties and attainable knowledge that can be obtained through conscious experience, refuting the theory that all knowledge is physical knowledge. If Mary looks at the wall and exclaims, “Oh, it’s blue!”, then this means that all of the physical knowledge Mary had obtained about the color blue while she was studying it was sufficient to tell her that she was experiencing the color when seeing it for the first time. And if Mary learns anything new by seeing the color blue, then we can conclude that qualia –individuals’ subjective experiences – are real properties, because there is a difference between black-and-white-world Mary and color-world Mary. However, if Mary doesn’t learn anything new from seeing blue, then we can say that there is no difference between a person who knows everything about a topic and a person who has experienced the topic. 

We can observe this concept in the making of artificial intelligence systems. Let’s say that all robots are essentially computers and unable to experience human feelings themselves. Will a robot that is trained extensively in counselling ever be able to replace a human counsellor? Assume the only difference is that the robot counsellor has never experienced the feelings of its clients before (e.g. sadness, depression, grief) while a human counsellor has experienced those feelings themselves.