Mary is a brilliant scientist who is, for whatever reason, forced to investigate the world from a black and white room via a black and white television monitor. This means she has never experienced anything in color, has seen the world only in black and white.
(Now, don't go about arguing that her skin is not black or white so she sees that - This is a hypothetical experiment, just imagine she is been seeing everything around her through a filter)
She specializes in the neurophysiology of vision and acquires, let us suppose, all the physical information there is to obtain about what goes on when we see ripe tomatoes, or the sky, and use terms like ‘red’, ‘blue’, and so on. She discovers, for example, just which wavelength combinations from the sky stimulate the retina, and exactly how this produces via the central nervous system. She knows everything there has to be in the world of physics and biology about the concept of 'color' but has never experienced it herself.
What will happen when Mary's screen malfunctions and a red apple is displayed? Will she learn anything or not?
This is the first time she experiences something she has known about for years. Does she learn anything new? Was there something that wasn't captured about the perception of color she hasn't been able to gain unless she saw the red apple?
Philosophers say that if Mary knew all the physical facts about color and seeing the red apple still thought her something new then mental states like color perception cannot be completely understood by physical facts.
This experiment presents what is called - THE KNOWLEDGE ARGUMENT
There are non-physical knowledge which can only be discovered through conscious experience.
This contradicts the theory of physicalism which states that everything in this world including mental states can be explained in physical facts.
These experiences have properties called QUALIA - These are subjective qualities that you can't accurately describe or measure. Qualia is unique to the person experiencing them.
When you read this story you might think this writer is just twisting an obvious fact. We haven't truly learned something unless we experience it. I might sit down and read everything there is to learn about making a dosa but my learning wouldn't be complete unless I make a dosa in real life. That seems like common sense, right? (My mother definitely thinks so)
Let me explain why this topic is the center for heated arguments among scientists.
Color perception is just a depiction of the various mental states and conscious experience.
Let's take for example what each and every student and scientist has been doing their entire life.
Studying from books
Have you ever opened a person up and seen the tiny insides of a neuron? Have you zoomed into the working of an atom and actually seen the electrons, protons, or its quantum workings? Have you gone and seen how a black hole pulls everything towards itself? To be honest, neither have a lot of scientists. But they base their researches and experiments on books and records, and other people use these findings to build new equipment or even medicines. So if the knowledge they use for their studies by itself is incomplete then how successful or useful will their experiments be?
But this also presents humans with an impossible predicament.
That a person can't become a nuclear physicist unless they have dissected an atom and seen an electron nor a space scientist unless they have gone to space, both either economically not possible or just not possible (owing to the fact no one has seen an electron)
Now what do you think is the solution to the problem? This is what scientists have been arguing for ages now and haven't reached a conclusion yet because this experiment has led to an existential crisis among scientists. Yikes, this just took a sad turn.
What started out to be a harmless hypothetical experiment has ended up raising some important questions among the scientist communities. Little did Mary know the havoc she wreaked.