In philosophy of mind, the knowledge argument (also known as Mary's Room, Mary the Colour Scientist, or Mary the super-scientist) is a thought experiment proposed by Frank Jackson in his article "Epiphenomenal Qualia" (1982), and extended in "What Mary Didn't Know" (1986). The thought experiment describes Mary, a scientist who exists in a black-and-white world where she has extensive access to physical descriptions of color, but no actual perceptual experience of color. Mary has learned everything there is to learn about color, but she has never actually experienced it for herself. The central question of the thought experiment is whether Mary will gain new knowledge when she goes outside of the colorless world and experiences seeing in color. The thought experiment is intended to argue against physicalism—the view that the universe, including all that is mental, is entirely physical. Jackson says that the "irresistible conclusion" is that "there are more properties than physicalists talk about". Jackson would eventually call himself a physicalist and say, in 2023, "I no longer accept the argument" though he feels that the argument should be "addressed really seriously if you are a physicalist". The debate that emerged following its publication became the subject of an edited volume, There's Something About Mary (2004), which includes replies from such philosophers as Daniel Dennett, David Lewis, and Paul Churchland.
Thought experiment
Mary is the second character put forward by Jackson in his article Epiphenomenal Qualia. The other is a gifted person called "Fred" who "has better colour vision than anyone else on record"; specifically, Fred can see two different colours of red where ordinary colour vision only sees one. The thought experiment was originally proposed by Jackson as follows:
There is disagreement about how to summarize the premises and conclusion of Jackson's argument in this thought experiment. Paul Churchland did as follows:
Mary knows everything there is to know about brain states and their properties. It is not the case that Mary knows everything there is to know about sensations and their properties. Therefore, sensations and their properties are not the same as (≠) the brain states and their properties. However, Jackson opposes it by saying that Churchland's formulation is not his intended argument. He especially objects to the first premise of Churchland's formulation: "The whole thrust of the knowledge argument is that Mary (before her release) does not know everything there is to know about brain states and their properties because she does not know about certain qualia associated with them. What is complete, according to the argument, is her knowledge of matters physical." He suggests his preferred interpretation:
Mary (before her release) knows everything physical there is to know about other people. Mary (before her release) does not know everything there is to know about other people (because she learns something about them on her release). Therefore, there are truths about other people (and herself) which escape the physicalist story. Later on, Amy Kind proposes another summary for the argument:
While in the room, Mary has acquired all the physical facts there are about color sensations, including the sensation of seeing red. When Mary exits the Room and sees a ripe red tomato, she learns a new fact about the sensation of seeing red, namely its subjective character. Therefore, there are non-physical facts about color sensations. [From 1, 2] If there are non-physical facts about color sensations, then color sensations are non-physical events. Therefore, color sensations are non-physical events. [From 3, 4] If color sensations are non-physical events, then physicalism is false. Therefore, physicalism is false. [From 5, 6]
Background Jackson says there are quite a few similar arguments that predate his formulation, even going back as far as John Locke. C. D. Broad, Herbert Feigl, and Thomas Nagel, over a fifty-year span, presented insight to the subject. Broad makes the following remarks, describing a thought experiment where an archangel has unlimited mathematical competences:
He would know exactly what the microscopic structure of ammonia must be; but he would be totally unable to predict that a substance with this structure must smell as ammonia does when it gets into the human nose. The utmost that he could predict on this subject would be that certain changes would take place in the mucous membrane, the olfactory nerves and so on. But he could not possibly know that these changes would be accompanied by the appearance of a smell in general or of the peculiar smell of ammonia in particular, unless someone told him so or he had smelled it for himself. In 1958, Feigl theorized that a hypothetical Martian, studying human behavior, will lack human sentiments. Nagel's essay "What Is It Like to Be a Bat?" takes a slightly different approach. He takes the perspective of humans attempting to understand the echolocation capabilities of bats. Even with the entire physical database at one's fingertips, humans would not be able to fully perceive or understand a bat's sensory system, namely what it is like to "see" the world through sound.
Implications Whether Mary learns something new upon experiencing color has two major implications: the existence of qualia and the knowledge argument against physicalism.
Qualia If Mary learns something new upon seeing red, it shows that qualia (the subjective, qualitative properties of experiences, conceived as wholly independent of behavior and disposition) exist. Therefore, it must be conceded that qualia are real, since there is a difference between a person who has access to a particular quale and one who does not.
Refutation of physicalism Jackson argues further, saying that if Mary does learn something new upon experiencing color, then physicalism is false. Specifically, the knowledge argument is an attack on the physicalist claim about the completeness of physical explanations of mental states. Mary may know everything about the science of color perception, but can she know what the experience of red is like if she has never seen red? Jackson contends that, yes, she has learned something new, via experience, and hence, physicalism is false.
Epiphenomenalism
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