Refuting Frank Jackson's Knowledge Argument

Refuting Jackson’s Knowledge Argument (Mary version)

In 1982, Frank Jackson outlined an argument against Physicalism, now popularly known as

the Knowledge Argument. He aimed to prove that there existed epiphenomenal qualia which

could not be described in terms related to the physical world. I will be seeking to object to

this argument in this paper. Jackson’s argument can be summarised as follows -

Mary is a brilliant scientist specialising in the neurophysiology of vision who is forced to

view the world from a monochromatic room via a black and white TV monitor. She acquires

all the possible physical information about colours and how we perceive them, including all

the scientific facts about how the brain understands wave-length combinations which

stimulate the retina. So, what will happen when Mary is released from her room or is given a

colour television monitor? It seems obvious that she will learn something about the world and

our visual experience of it. But in such a case, as Jackson says, “But then it is unescapable

that her previous knowledge was incomplete. But she had all the physical information. Ergo

there is more to have than that, and Physicalism is false.” 

This argument can be reconstructed in the standard Premise-Conclusion form as follows –

Premise 1: Mary has never seen any colours, but she has all the physical information about


Premise 2: When Mary sees a colour for the first time, she learns something about colours

and how we perceive the world.

Premise 3: If Mary knows all the physical information and facts about colours, but she still

learns something about them on seeing one for the first time; then colours have non-physical


Conclusion: Colours have non-physical properties.

Premise 4: If colours have non-physical properties, then physicalism is false.

Conclusion: Ergo, physicalism is false.

Premise 1 states that Mary, despite never having seen any colours, knows all the physical

information there is to know about colours. According to Premise 2, when Mary sees a colour

for the first time, she learns something. Premise 3 lays out that if Mary knows all the physical

information there is to know about colours but still learns something about them on seeing

them for the first time, then there is some information about colours which is non-physical.

From these three premises, we can derive a conclusion that colours have non-physical

properties. Premise 4 proposes a condition that if colours have non-physical properties, then

physicalism — the idea that everything that exists is nothing more than its physical properties

and that the only existing substance is physical — is false. From the previous conclusion and

Premise 4, we can derive that physicalism is false.

In Premise 2, we assume that Mary learns something new about colours on seeing them for

the first time. I would like to refute this by saying that instead, all Mary does is realise a fact

she already knows. She already knows all the relevant facts about say, the colour of the grass,

and how humans view it. So, all she does is see another representation of the fact like, “Oh,

the grass is green.” This form of phenomenal knowledge or concepts can only be learnt

through first-hand experiences, but they are physical properties of objects. The phenomenal

blueness of the sky is a phenomenal property of the sky. But Mary already knew the facts

which make this new knowledge true before her release, in another way. Another example of

this would be a man who knows that there is oxygen and carbon dioxide in the air that he is

breathing but might fail to recognise that there is O2 and CO2 in the atmosphere till it is

pointed out to him. Or simply, a woman who can feel pain, but would not realise her Parietal

Insular Cortical Neurons (PCINs) are firing unless it is explained to her.

Jackson might object to this argument by pointing out that Mary is supposed to know all

possible physical information and facts about colours and human vision before she leaves the

room. So, if she doesn’t, this means that whatever new knowledge she gains cannot be

knowledge of physical properties.

I would like to reply to this by explaining that no amount of information about physical or

even non-physical properties could explain to Mary what seeing a colour is like. However,

this does not mean that her knowledge is incomplete. Even if she knows all the physical

properties of a colour, there is a possibility of her being unable to understand physical

properties like colours before experiencing them for herself. I would argue that while Mary

might have all the necessary knowledge of physical properties, to be able to understand the

phenomenal properties among them would require her to experience them. Simply reading

records of physical facts of being in pain, and how the brain processes it, would not let a

doctor understand it himself without experiencing it. But this does not mean that the doctor

did not know all possible facts about pain beforehand under another description or realisation.

I would like to conclude by suggesting that Jackson’s Knowledge Argument does not

disprove physicalism, but instead it simply helps physicalists realise that there exist

phenomenal physical properties which need experience for their understanding, when realised

as phenomenal concepts such as colour even if we understand them in another way