Knowledge Argument and its Implications


Jackson's Knowledge Argument

David Chalmers and Hard Problem of Consciousness

When you look at this page, there is a whir of processing: photons strike your retina, electrical signals are passed up your optic nerve and between different areas of your brain, and eventually you might respond with a smile, a perplexed frown or a remark. But there is also a subjective aspect. When you look at the page, you are conscious of it, directly experiencing the images and words as part of your private, mental life. You have vivid impressions of colored flowers and vibrant sky. At the same time, you may be feeling some emotions and forming some thoughts. Together such experiences make up consciousness: the subjective, inner life of the mind.

The Hard Problem

Researchers use the word “consciousness” in many different ways. To clarify the issues, we first have to separate the problems that are often clustered together under the name. For this purpose, I find it useful to distinguish between the “easy problems” and the “hard problem” of consciousness. The easy problems are by no means trivial – they are actually as challenging as most in psychology and biology – but it is with the hard problem that the central mystery lies.

The easy problems of consciousness include the following: How can a human subject discriminate sensory stimuli and react to them appropriately? How does the brain integrate information from many different sources and use this information to control behavior? How is it that subjects can verbalize their internal states? Although all these questions are associated with consciousness, they all concern the objective mechanisms of the cognitive system. Consequently, we have every reason to expect that continued work in cognitive psychology and neuroscience will answer them.

The hard problem, in contrast, is the question of how physical processes in the brain give rise to subjective experience. This puzzle involves the inner aspect of thought and perception: the way things feel for the subject. When we see, for example, we experience visual sensations, such as that of vivid blue. Or think of the ineffable sound of a distant oboe, the agony of an intense pain, the sparkle of happiness or the meditative quality of a moment lost in thought. All are part of what I am calling consciousness. It is these phenomena that pose the real mystery of the mind.

Knowledge Argument

To illustrate the distinction, consider a thought experiment called “The Knowledge Argument” devised by the Australian philosopher Frank Jackson.

According to the knowledge argument, there are facts about consciousness that are not deducible from physical facts. Someone could know all the physical facts, be a perfect reasoner, and still be unable to know all the facts about consciousness on that basis.

Frank Jackson’s canonical version of the argument provides a vivid illustration. On this version, Mary is a neuroscientist who knows everything there is to know about the physical processes relevant to color vision. But Mary has been brought up in a black-and-white room (on an alter-native version, she is colorblind) and has never experienced red. Despite all her knowledge, it seems that there is something very important about color vision that Mary does not know: she does not know what it is like to see red. Even complete physical knowledge and unrestricted powers of deduction do not enable her to know this. Later, if she comes to experience red for the first time, she will learn a new fact of which she was previously ignorant: she will learn what it is like to see red.

Let me try to explain the argument again in different words.

Suppose that Mary, a neuroscientist in the 23rd century, is the world’s leading expert on the brain processes responsible for color vision. But Mary has lived her whole life in a black-and-white room and has never seen any other colors. She knows everything there is to know about physical processes in the brain – its biology, structure and function. This understanding enables her to grasp everything there is to know about the easy problems: how the brain discriminates stimuli, integrates information and produces verbal reports. From her knowledge of color vision, she knows the way color names correspond with wavelengths on the light spectrum. But there is still something crucial about color vision that Mary does not know: what it is like to experience a color such as red. It follows that there are facts about conscious experience that cannot be deduced from physical facts about the functioning of the brain.

Jackson’s version of the argument can be put as follows (here the premises concern Mary’s knowledge when she has not yet experienced red):


(1) Mary knows all the physical facts.
(2) Mary does not know all the fact
(3) The physical facts do not exhaust all the facts.


There are following very important implications of “Knowledge Argument”:

  1. Human Subjective Experiences as Phenomena are Not some illusionary phenomena. They are as real as anything else.
  2. Human Subjective Experiences “In Principle” cannot be captured in the Structural, Functional, Procedural, Material Information, even if the information is in the highest possible detail.
  3. Human Subjective Experiences “In Principle” can NOT be reduced in the Structural, Functional, Procedural, Material Information, even if the information is in the highest possible detail. This also implies that all the reductionist explanations of Consciousness are False!
One can put the knowledge argument more generally:

(1) There are truths about consciousness that are not deducible from physical truths.
(2) If there are truths about consciousness that are not deducible from physical truths, then materialism is false.
(3) Materialism is false.


Indeed, nobody knows why these physical processes are accompanied by conscious experience at all. Why is it that when our brains process light of a certain wavelength, we have an experience of deep purple? Why do we have any experience at all? Could not an unconscious automaton have performed the same tasks just as well? These are questions that we would like a theory of consciousness to answer.

One should definitely watch following TED Talk by David Chalmers in order to understand the Hard Problem of Consciousness.


And in order to research further on the topic, following resource by David J Chalmers is a MUST Read. It shows various issues in Mind Problem and concludes how “Hard Problem of Consciousness” is still unsolved and points towards the possibility that probably “Consciousness” may be an ontologically distinct entity.

Consciousness and Its Place in Nature — David J Chalmers


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