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Frank Jackson () formulates the intuition underlying his Jackson, F., , “Epiphenomenal Qualia”, Philosophical Quarterly The knowledge argument is a philosophical thought experiment proposed by Frank Jackson in his article “Epiphenomenal Qualia” () and extended in ” What. Jackson opens his essay with a definition: “It is undeniable that the physical, chemical and biological sciences have provided a great deal of information about .

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The knowledge argument aims to establish that conscious experience involves non-physical properties. It rests on the idea that someone who has complete physical knowledge about another conscious being might yet lack knowledge about how it feels to have the experiences eliphenomenal that being.

It is one of the most discussed arguments against physicalism. In the context of his explanation of the difference between mechanistic and emergentist theories, C. Feigl briefly discusses the epistemic limitations of a Martian who studies human behavior but does not share human sentiments:. As these examples suggest, the idea that complete physical knowledge isn’t sufficient ajckson complete knowledge of phenomenal states has been around for a epiphenonenal.

In many of these cases, the idea is not used to argue directly against physicalism, although such a use is arguably present in Broad The jacmson debate was initiated by Jackson who used the idea to develop a more explicit anti-physicalist argument, the knowledge argument.

Frank Jackson formulates the intuition underlying his Knowledge Argument in a much cited passage using his epiphenomena, example of the neurophysiologist Mary:. Most authors who discuss the knowledge argument cite the case of Mary, but Frank Jackson used a further epipyenomenal in his seminal article: We might want to know what color Fred experiences when looking at things that appear to him in that particular way.

It seems clear that no amount of knowledge jafkson what happens in his brain and about how color information epiphenomenl processed in his visual system will help us to find an answer to that question. In both cases cited by Jackson, an epistemic subject A appears to eppihenomenal no access to particular items of knowledge about a subject Epipgenomenal A cannot know that B has an experience of a particular quality Q on certain occasions.

This particular item of knowledge about B is inaccessible to A because A jwckson had experiences of Q herself. The argument may thus be reformulated in two different ways:. The conclusion of the stronger version of qualix argument 3b is an ontological claim that the physicalist must reject. The conclusion of the weaker version of the argument is merely an epistemological claim that is compatible with denying the existence of non-physical facts. Although Jackson’s original formulation in terms of information is open to both interpretations it is clear that the second stronger version is what he had in mind.

As many have pointed out, the result of the weaker version 3a does not imply the result of the stronger version 3b. That a person has incomplete knowledge about a certain topic does not imply without further assumptions that there is some specific fact she does not have knowledge of.

The example of knowledge about oneself de se knowledge may illustrate the general point. John’s knowledge concerning the present location of people is incomplete. He lacks a specific locating piece of de se knowledge. Still, there need not be any fact concerning the location of people that John does not have knowledge of. It does not follow from the description of the case that John does not have knowledge of the fact that John is in Amsterdam. John may well know that John is in Amsterdam but, having forgotten that he is himself John, he may fail to conclude that he is now in Amsterdam.

If John finally learns that he is in Amsterdam, he does not thereby learn a new fact—or so many philosophers would insist—he gains new knowledge of a fact that he already knew in a different way.

Qualia: The Knowledge Argument

Many authors accept the weaker version of the argument but reject the stronger one for the reason just sketched: These authors accept the first premise of both versions of the argument and the second premise of the first epiphenomenap as well, but they deny the second premise of the second version and insist that 2a does not imply 2b.

Others deny even the weaker version V1 and claim that Mary does not qulia any new propositional knowledge no new knowledge about something that is the case, no factual knowledge. To locate the different points of disagreement it jsckson helpful to formulate the stronger version of the argument more explicitly. Once C1 and C2 are accepted, there is obviously no way to avoid C3 which follows logically from the former two.

Moreover, is seems hard to deny that it is in principle possible to have complete physical knowledge about human color vision or about an appropriately chosen part thereof. If so, premise P1 should be accepted as an appropriate description of a legitimate thought experiment. To avoid the antimaterialist conclusion C3 the physicalist can a object against the inference from P1 to C1 a minority of philosophers have chosen this strategy, see Section 4.


The knowledge argument is often cited as one of those anti-physicalist qualia-based arguments that are supposed to justify property dualism. The above formulation, however, does not explicitly mention non-physical properties but only non-physical facts.

Knowledge argument

But the relation between the two claims is obvious. Friends of the knowledge argument will say that the facts at issue are non-physical because they involve the exemplification of non-physical properties e. It would be natural to define physical facts as those facts that can be expressed in this way. It is common to formulate Mary’s new knowledge in terms of Thomas Nagel’s famous locution of knowing what it’s like: Mary does not know while living in her black-and-white environment what it is like to see colors and she learns what it is like to see colors only after her release.

But this common way to put the point may lead to a confusion of a mere acquaintance with kinds of color experiences by having and remembering them and b knowledge about what kind of color experience other subjects have at a given occasion, and it may thereby lead to a failure to distinguish two steps of epistemic progress that Jackson’s Mary takes at once.

Like Mary, Marianna first at t 1 lives in a black and white environment.

Contrary to Mary at a later moment t 2 she gets acquainted with colors by seeing arbitrarily colored objects abstract paintings, red chairs, blue tables, etc. Marianna is therefore unable to relate the kinds of color experiences she now is acquainted with to what she already epiphenoemnal about them at t 1.

At t 2Marianna may wonder which of four slides a red, a blue, a green and a yellow slide appears to her in the color normal people experience when looking at the cloudless sky. At t 2 Marianna knows, in a sense, what it is like to have experiences of red, blue, etc. But she still lacks the relevant items of knowledge about what other people experience: Only at t 3when Marianna is finally released and sees the sky, does she gain this item of knowledge.

One epiphenoemnal to describe the two steps of epistemic progress is this: By acquiring these concepts she acquires the capacity to ask new questions, and to form new eventually false hypotheses e. Only at t 3 does she acquire the kind of knowledge that the knowledge argument is concerned with knowledge that involves the application of phenomenal concepts qualiz experiences of other people. Once these two steps are clearly distinguished one may conclude that Marianna’s relevant epistemic progress at t 3 and Mary’s relevant progress after release is not happily described by talk of knowing what it’s like.

Rather, or so one may argue, Mary and Marianna acquire a particular kind of belief that the sky appears blue to normal perceivers, namely the phenomenal belief that it appears blue to normal perceivers, where phenomenal belief involves the application of the appropriate phenomenal concept. Both may have believed, in a sense the non-phenomenal sense that does not require use uqalia phenomenal concepts that the sky appears blue to normal perceivers while still in their black-and-white environment they may have been told so by their friends.

For the distinction between phenomenal and non-phenomenal belief see Nida-Rumelin and Some authors have raised doubts about the thought experiment itself.

Knowledge argument – Wikipedia

It is sometimes pointed out, for example, that merely confining Mary to a monochromatic environment would not prevent her from having color experiences see Thompsonor that, after release, she would not be able to see colors. But the example can be refined to meet these objections. Mary might be monochromatic from birth and changed into a normal perceiver by some medical procedure. It is sometimes objected that already accepted or future results of visual science are or might be incompatible with the existence of a Mary-case a person with monochromatic experience who becomes a normal color perceiver later or that such results might require to preserve consistence with visual science the introduction of so many additional assumptions that the conceivability of the example becomes doubtful.

To this one might reply that the thought experiment need not be compatible with visual science.

If the case of a person with monochromatic vision who turns into a normal perceiver really does involve serious difficulties for materialism, then the mere fact if it were one that our visual apparatus excludes the actual existence of such a case does not seem to provide a convincing reply for the materialist.

But this point the relevance or irrelevance of visual science in this context has not received much discussion in the literature. It has, however, been pointed out see Graham and Horgan,footnote 4 with its reference to Shepard that at least presently available results of color vision science do not exclude a Mary-case.


The psychologist Knut Nordby was a real life case of a color vision specialist who was also a complete achromat. Another doubt about the thought experiment is raised by the claim that a person who is confined to a monochromatic environment but knows everything physical there is to know about visual color experience would be able to figure out what colored things look like and thus would e. Dennett ; Dennett ; Churchland ; Maloney Probably the most common reaction to this is simply to doubt the claim.

But it is not clear that the claim, if correct, would undermine the knowledge argument. The opponent would have to show that complete physical knowledge necessarily involves the capacity to imagine blue. One may doubt that this claim is compatible with the widely accepted assumption that physical knowledge can be acquired independently of one’s particular perceptual apparatus.

Arguably a subject whose visual apparatus is not suited for visual experiences at all will not be able to develop the capacity to imagine colors on the basis of physical knowledge alone, even if this were true for Mary. Some have argued that Mary would recognize the colors when first seeing them on the basis of her complete physical knowledge about color vision see Hardin A possible and common response is to simply doubt these claims.

But, in any case, it is not clear that these claims undermine the knowledge argument. One may respond along the following lines: If Mary when first confronted with red were able to conclude that she is now seeing what people call red, she thereby acquires a large set of new beliefs about red experiences that they are produced by roses, such-and-such wavelength combinations and so on. On the basis of seeing red she a acquires a new phenomenal concept of red and b she forms new beliefs involving that new concept using her previously acquired physical knowledge.

But if this description is correct, then her previous knowledge was incomplete for a detailed discussion of Dennett’s argument involving the blue banana trick see Dale It may appear obvious that premise P1 Mary has complete physical knowledge about human color vision implies C1 Mary knows all the physical facts about human color vision.

If all physical facts can be known under some physical conceptualization, then a person who has complete physical knowledge about a topic knows all the relevant physical facts.

But a few philosophers can be understood as objecting against precisely this apparently unproblematic step.

Harman argues that Mary does not know all the functional facts concerning human color vision because she lacks the concept of what it is for an object to be red, blue, etc. Flanagan distinguishes metaphysical physicalism from linguistic physicalism.

Alter points out that the knowledge argument needs the premise that all physical facts can be learned discursively and argues that this assumption has not been established. It may be argued against this view that it becomes hard to understand what it is for a property or a fact to be physical once we drop the assumption that physical properties and physical facts are just those properties and facts that can be expressed in physical terminology.

Two different versions of the No Propositional Knowledge -View have been proposed. According to the Ability Hypothesis most prominently defended in Lewisand in Nemirow, epiphenomeanl, Mary jacksoon not acquire any new propositional knowledge after release no knowledge about something that is the case, no factual knowledgebut only a bundle of abilities like the ability to imagine, remember jqckson recognize colors or color experiences.

Lewis and Nemirow presuppose that Mary’s epistemic progress after release consists in the acquisition of knowing what it is like e. Lewis’s main quwlia for the Ability Hypothesis can be summarized like this. According to the HPI knowing what it is epiphenomeal is propositional in the following sense: The Ability Hypothesis should be preferred. Note that the Ability Hypothesis is compatible with the view that we do sometimes acquire propositional knowledge on the basis of getting acquainted with a new kind of experience from the first person perspective.

The following remarks by Levin are hard to deny:. But, as pointed out by Tyethis does not undermine the Ability Hypothesis. The Ability hypothesis implies that there is some knowledge that can only be acquired by having experiences of jafkson particular kind and that this knowledge is nothing but knowing-how.