DE Weekly: Frank Jackson, Physicalism, & Mary’s Room
Below is an archived email originally sent on August 24, 2026.
Frank Jackson, Physicalism, & Mary’s Room
Last week, I wrote about Thomas Nagel’s 1971 essay “What Is It Like to Be A Bat?”. I emphasized how one of the conclusions of the essay is that we cannot fully understand everything if we use only a physicalist, materialist lens; some things require a deeper understanding of mind and consciousness.
Today, I’m going to introduce you to a thought experiment that reinforces this notion. It was invented by Australian philosopher Frank Jackson and is called “Mary’s Room.” It is one of the strongest challenges to reductionist physicalism and an interesting foray into the philosophy of mind.
The “Mary’s Room” thought experiment is set up as such: Mary, a brilliant scientist, lives in a room that only has black and white, no color.
She learns all of the physical facts about human vision and about colors through reading black-and-white books and watching black-and-white screens. She even knows every detail of what happens physically in a person’s brain when they see colors like red or blue.
One day, Mary leaves her room and sees a bright red tomato. Upon seeing the tomato, has Mary learned something new?
There are two possible answers to this thought experiment.
First, the purely physicalist response: no, she has learned nothing new. She already possessed the knowledge of what “red” was, and so merely gained another way of interpreting knowledge she already had.
The second answer: yes, she has learned something new. Despite reading physical books and watching television all in black-and-white, Mary never experienced the subjective perception of what “red” actually feels like.
This latter answer is the one that Jackson himself espouses, and one which I, myself, would espouse were I asked to choose between the two.
Similarly to what I covered last week––how it is impossible to imagine what it is like to be a bat––I believe the same principle applies to Mary’s Room.
If you had grown up in a world of black-and-white and never seen another color before, seeing a bright red tomato for the first time would be an experience nothing short of astounding.
Therefore, if we are to adopt the position of Jackson, this disproves rigid physicalism, since we must accept that we cannot know everything there is to know about the world only through physical science; the philosophy of mind and consciousness must be considered.
It means, too, that there are certain non-physical truths or properties of life that contain more than physical processes in the brain and body (as I have written about before concerning The Hard Problem and the Mind-Body Problem).
The Mary’s Room thought experiment aims to prove the existence of qualia, an internal, subjective sense of perception about experiences, or the what-it-is-like of being or of experiencing a thing.
I believe that the Existentialists would agree with that aim.
Jean-Paul Sartre wrote that we cannot understand the breadth and depth of human emotion and experience until we actually live them ourselves. We could read all about death, grief, relationships, tragedy, and war, but know absolutely nothing about them until we actually experience any of them ourselves.
Just as Mary had a physicalist idea of what a red tomato looks like but could not understand the redness of it until seeing it.
Mary was expert in the physicalist workings of the objective world, but she was woefully limited in her understanding of the subjective world.
Just as the Existentialists would say that there is an inner depth only understood through the phenomenological experiences of the consciousness of each Self.
When Mary left the familiarity of her room, I imagine her entire worldview must have expanded. It must have been an existential awakening akin to that of the escapee from Plato’s Cave, taking a leap from the purely physical to a world full of extra-physical, subjective beauty and wonder.
Mary’s move out of her room and into the world is symbolic of the move each of us must make at some point in our lives from the physical and material into the phenomenological and authentic, if we are curious about such questions as the hard problem of consciousness.
“Science manipulates things and gives up living in them. It makes its own limited models of things; operating upon these indices or variables to effect whatever transformations are permitted by their definition, it comes face to face with the real world only at rare intervals. Science is and always will be that admirably active, ingenious, and bold way of thinking whose fundamental bias is to treat everything as though it were an object-in-general - as though it meant nothing to us and yet was predestined for our own use.” ― Maurice Merleau-Ponty, Eye and Mind
Thanks for reading.
Sincerely,
Brandon J. Seltenrich
P.S.––
Thought experiments are always fun to explore and opine on. If there are any personal favorites that you would like to see covered, let me know.
P.P.S.–
This marks two years since I began the newsletter. 104 straight weeks of a new newsletter on a new topic each Monday morning. Thank you so much.
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