## 1. History of the Underlying Ideas



The Knowledge Argument became the subject of intense philosophical
discussion following its canonical formulation by Frank Jackson
(1982). However, there are numerous precursors of this argument in the
literature. Precursors of the Knowledge Argument typically involve at
least one of two strategies which are familiar from Jackson's
formulation. The first is to appeal to what Daniel Stoljar & Yujin
Nagasawa term the *knowledge intuition*: the intuition that no
amount of knowledge of the physical information or physical facts
concerning certain experiences can by itself suffice for knowledge of
what these experiences are like, i.e., knowledge of their qualitative
character or distinctive qualia (2004, 2-3). The second is to
make use of thought experiments which are similar to Jackson's
famous example of Mary. These thought-experiments typically involve a
being who has complete knowledge of the physical information or
physical facts concerning certain experiences, but who (it is claimed)
lacks knowledge of what those experiences are like.



As examples of the knowledge intuition, Stoljar & Nagasawa cite
passages by Bertrand Russell (1998, 13-14) and by J.W. Dunne
(1929). As Dunne puts it, quoting James Ward, physical descriptions
cannot entail knowledge of what it is that "you immediately
experience when you look at a field poppy" (1929, 5). Around the
same time as Dunne was writing, C.D. Broad (1925) used a
thought-experiment as part of an argument against a mechanistic
version of physicalism. Broad argues that even if the mechanistic
theory of chemistry were true there still would be a property of
ammonia that a mathematical archangel endowed with unlimited
mathematical skills and "gifted with the further power of
perceiving the microscopic structure of atoms" could not
predict, namely its smell:



> 
> He [the archangel] 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
> theses 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 (1925,
>  71).[1]
> 



Under the title "The Cognitive Role of Acquaintance," H.
Feigl (1958) briefly discusses the epistemic limitations of a Martian
who studies human behavior but does not share human sentiments:



> 
> The first question I wish to discuss concerns the cognitive
> 'plus', i.e., the alleged advantages of knowledge by
> acquaintance over knowledge by description. We may ask, for example,
> what does the seeing person know that the congenitally blind person
> could not know. Or, to take two examples from Eddington, what could a
> someone know about the effects of jokes if he had no sense of humor?
> Could a Martian, entirely without sentiments of compassion and piety,
> know about what is going on during a commemoration of the armistice?
> For the sake of argument, we assume complete physical predictability
> and explainability of the behavior of humans equipped with vision, a
> sense of humor, and sentiments of piety. The Martian could then
> predict all responses, including the linguistic utterances of the
> earthlings in the situations which involve their visual perceptions,
> their laughter about jokes, or their (solemn) behavior at the
> commemoration. But *ex hypothesi*, the Martian would be lacking
> completely in the sort of *imagery* and *empathy* which
> depends on familiarity (direct acquaintance) with the kinds of
> *qualia* to be imaged or empathized (1958, 431).
> 



B. A. Farrell had earlier presented a similar thought experiment
featuring a Martian; in this version, it is humans who lack knowledge
of what it is like for the Martian to exercise his sensory capacities
(1950, 183; though Farrell ultimately argues that this thought
experiment does not present a challenge to physicalism). Paul E.
Meehl, responding to Feigl, describes two individuals who each have
complete neurophysiological knowledge, one of whom is congenitally
blind; he takes it as intuitive that this person does not know
something which the other does, namely "what red looks
like" (1966, 151).



More recent examples from the literature come closer to being versions
of the Knowledge Argument rather than merely precursors to it. For
example, consider the following statement of the knowledge intuition
by Nicholas Maxwell:



> 
> from a complete physicalist description alone it would be impossible
> to deduce the perceptual qualities of things, but this is due, not to
> the fact that things do not really possess perceptual qualities, but
> to the fact that the physicalist description is incomplete: it does
> not tell us all that there is to know about the world. It does not
> tell us what it is like to be a human being alive and experiencing in
> the world (1965,
>  309).[2]
> 



And Howard Robinson, writing the same year as Jackson published
'Epiphenomenal Qualia', describes a deaf scientist
"who knows everything there is to know about the physical
processes involved in hearing", but who intuitively does not
know what it is like to hear (1982, 4).



Finally, it is worth mentioning the extremely influential thought
experiment described by Thomas Nagel (1974). According to Nagel, the
physical facts about an organism and its perceptual systems are
"objective facts *par excellence* - the kind that
can be observed and understood from many points of view and by
individuals with differing perceptual systems" (1974, 442).
Nagel argues that even if we knew all the objective facts about a
bat's sonar system, we would still not know what it would be like to
perceive using this system. Therefore, complete knowledge of the
physical facts about a bat's perceptual system would not yield
knowledge of certain facts about a bat's experiences; these facts
can only be captured from a subjective perspective. Nagel does not
argue against physicalism, but rather claims that we presently have no
understanding of how it can be true. In Section 4.9, we shall outline
a related approach to the knowledge argument which interprets it as a
challenge not to physicalism but to a position called objectivism.


## 2. The Basic Idea



Frank Jackson (1982) formulates the intuition underlying his Knowledge
Argument in a much cited passage using his famous example of the
neurophysiologist Mary:



> 
> Mary is a brilliant scientist who is, for whatever reason, forced to
> investigate the world from a black and white room via a black and
> white television monitor. She specializes in the neurophysiology of
> vision and acquires, let us suppose, all the physical information
> there is to obtain about what goes on when we see ripe tomatoes, or
> the sky, and use terms like 'red', 'blue', and
> so on. She discovers, for example, just which wavelength combinations
> from the sky stimulate the retina, and exactly how this produces
> *via* the central nervous system the contraction of the vocal
> chords and expulsion of air from the lungs that results in the
> uttering of the sentence 'The sky is blue'.... What
> will happen when Mary is released from her black and white room or is
> given a color television monitor? Will she *learn* anything or
> not? It seems just obvious that she will learn something about the
> world and our visual experience of it. But then is it inescapable 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.
> 



The argument contained in this passage may be put like this:



> 
> (1) Mary has all the physical information concerning human color
> vision before her release.
> 
> 
> (2) But there is some information about human color vision that she
> does not have before her release.
> 
> 
> 
> Therefore
> 
> 
> 
> (3) Not all information is physical information.
> 
> 
> 



Most authors who discuss the knowledge argument cite the case of Mary,
but Frank Jackson used a further example in his seminal article: the
case of a person, Fred, who sees a color unknown to normal human
perceivers. 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 about what happens in his brain and
about how color information is 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 have no access to
particular items of knowledge about a subject *B*: *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* never had experiences of *Q* herself.


## 3. Some Clarifications


### 3.1 Two Versions of the Argument



As Horgan (1984) points out, talk of 'physical
information' in the context of the knowledge argument is
ambiguous between an epistemological and an ontological reading.
"Physical information" may be interpreted (a) in the sense
of what Horgan calls 'explicit physical information'
(according to Horgan's proposal a sentence *S* expresses
explicit physical information about certain processes just in case
*S* belongs to, or follows from, a theoretically adequate
physical account of those processes) or (b) in the sense of
'ontologically physical information' which is explicated
in Horgan (1984, 150) as follows: a sentence *S*
"expresses ontologically physical information about certain
processes just in case (i) all entities referred to or quantified over
in *S* are physical entities, and (ii) all the properties and
relations expressed by the predicates in *S* are physical
properties and relations." Presupposing a distinction along
these lines one may replace 'to have all explicit physical
information about *x*' by 'to have complete
physical knowledge about *x*' and one may replace
'to have all ontologically physical information about
*x*' by 'to know all the physical facts about
*x*'. The argument may thus be reformulated in two
different ways:



**(V1) The weaker version of the knowledge argument**:
  


(1a) Mary has complete *physical knowledge* concerning facts
about human color vision before her release.



(2a) But there is some *kind of knowledge* concerning facts
about human color vision that she does not have before her
release.



Therefore



(3a) There is some *kind of knowledge* concerning facts about
human color vision that is non-physical knowledge.



**(V2) The stronger version of the knowledge argument**:
  





(1b) Mary knows all the *physical facts* concerning human color
vision before her release.



(2b) But there are *some facts* about human color vision that
Mary does not know before her release.



Therefore



(3b) There are *non-physical facts* concerning human color
vision.




The conclusion of the stronger version of the 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. Let us suppose that John,
who is at *t* in Amsterdam, does not know that he is now in
Amsterdam (if asked about his present location he would assert
"I am now in Venice"). 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.



If - in analogy to the *de se* case - some physical
facts about color vision can be known in two different ways, - in
a 'physical way' (under 'physical concepts')
and in some other, non-physical way (under 'non-physical
concepts'), then it is possible to acquire new (non-physical)
knowledge about a (physical) fact without thereby acquiring knowledge
of a new fact (the very same fact may have been known before under its
physical conceptualization). Many authors accept the weaker version of
the argument but reject the stronger one for the reason just sketched:
they admit that Mary gains new propositional knowledge but deny that
she thereby comes to know facts that she did not know before in some
other way. (These authors accept the first premise of both versions of
the argument and the second premise of the first version as well, but
they deny the second premise of the second version and insist that
(2a) does not imply (2b)). Their position with respect to the
knowledge argument will be called the *New Knowledge/Old
Fact-View* (see
 Section 4.6
 below). Others deny even the weaker version V1 and claim that Mary
does not gain any new propositional knowledge (no new knowledge about
something that is the case, no factual knowledge). Their position will
be called the *No Propositional Knowledge View* (see
 Sections 4.3
 and
 4.5
 below).



To locate the different points of disagreement it is helpful to
formulate the stronger version of the argument more explicitly.



**(V3) Explicit formulation of the knowledge argument (stronger
version)** :


|  |  |
| --- | --- |
| *Premise P1* | Mary has complete physical knowledge about human
color vision before her release.


Therefore |
| *Consequence C1* | Mary knows all the physical facts about human color
vision before her release. |
| *Premise P2* | There is some (kind of) knowledge concerning facts
about human color vision that Mary does not have before her release.


Therefore (from (P2)): |
| *Consequence C2* | There are some facts about human color vision that
Mary does not know before her release.


Therefore (from (C1) and (C2)): |
| *Consequence C3* | There are non-physical facts about human color
vision. |




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 4.2
 below) or he or she can avoid C2 by (b) denying premise P2 (this is
the strategy chosen by proponents of the *No Propositional
Knowledge View*, see Sections
 4.3
 and
 4.5
 below) or by (c) blocking the inference from premise P2 to C2 (this
is the strategy chosen by a majority of physicalist philosophers who
subscribe to some version of the *New Knowledge/Old Fact View*,
see
 Section 4.6
 below).


### 3.2 Physical and Non-physical



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. 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.g. of
the property of having an experience with quality *Q*).



In the assumption that Mary has all physical knowledge (first version)
or knows all the physical facts (second version)
"physical" is meant in a very broad sense that includes
knowledge about (or facts concerning) the functioning of the receptors
and neurons involved in color vision (biological and physiological
knowledge/facts) as well as knowledge about (or facts concerning) the
whole network of causal relations between processes underlying color
vision, external stimuli and behavior (functional knowledge/
functional facts). "Physical" knowledge in the broad sense
at issue even includes psychological knowledge (e.g. knowledge about
the result of psychophysical experiments) in so far as they can be
formulated without use of phenomenal terminology. One might try to
explicate "physical knowledge" in the sense at issue in
roughly the following way: physical knowledge includes all knowledge
that is expressible in a terminology that does not contain irreducibly
mental terms. It would be natural to define physical facts as those
facts that can be expressed in this way. But note that this definition
of 'physical facts' begs the question against an objection
that has been raised against the knowledge argument (see
 Section 4.2
 below). It is certainly not easy to formulate a precise, adequate and
non question-begging account of "physical knowledge" and
"physical facts" suited for the discussion of the
knowledge argument. It is, however, quite common to assume that our
intuitive understanding of "physical knowledge" in the
broad sense at issue is clear enough for the purposes of the debate,
though some argue that talk of "physical facts" needs
clarification (see Alter 1998).


### 3.3 Knowing what it is like



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. To see the two steps involved one may consider an
example used in Nida-Rumelin (1996) and (1998): Like Mary,
Marianna first (at *t1*) lives in a black and white
environment. Contrary to Mary (at a later moment
*t2*) she gets acquainted with colors by seeing
arbitrarily colored objects (abstract paintings, red chairs, blue
tables, etc. but no yellow bananas, no pictures of landscapes with a
blue sky etc.). Marianna is therefore unable to relate the kinds of
color experiences she now is acquainted with to what she already knew
about them at *t1*. At *t2*,
Marianna 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 *t2* 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: there is a clear sense in which she still may
not know *that* the sky appears blue to normal perceivers, she
may even have the false belief that it appears to normal perceivers
like the red slide appears to her and thus believe, in a sense, that
the sky appears red to normal perceivers. Only at
*t3*, when Marianna is finally released and sees the
sky, does she gain this item of knowledge. One way to describe the two
steps of epistemic progress is this: At *t2*, by
having color experiences, Marianna can form new concepts, she now has
what has been called 'phenomenal concepts' of kinds of
color experiences. By acquiring these concepts she acquires the
capacity to ask new questions, and to form new (eventually false)
hypotheses (e.g. about the appearance of the sky to normal
perceivers). Only at *t3* does she acquire the kind
of knowledge that the knowledge argument is concerned with (knowledge
that involves the application of phenomenal concepts) about
experiences of other people.



Once these two steps are clearly distinguished one may conclude that
Marianna's relevant epistemic progress at *t3* (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 of 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 1996 and
1998).


## 4. Objections


### 4.1 Doubts about the Thought Experiment



Some authors have raised doubts about the thought experiment itself.
It is sometimes pointed out, for example, that merely confining Mary
to a monochromatic environment would not prevent her from having color
experiences (see Thompson 1995, 264) or 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,
2000, footnote 4 with its reference to Shepard 1993) 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. See his
paper 'Vision in a Complete Achromat: A Personal Account',
linked into in the Other Internet Resources section and Nordby,
2007.)



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.g. be able to imagine the kind of color experience produced in
normal perceivers when looking at the cloudless sky during the day
(see e.g. Dennett 1991; Dennett 2007; Churchland 1989; Maloney 1985,
36). 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 1992). According to this claim she would
think something like "oh, so this is red" when first
confronted with a red patch and she could not be fooled by what
Dennett calls 'the blue banana trick': when shown a blue
banana she would know that it has the wrong color (see Dennett 1991).
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 1995).


### 4.2 Complete Physical Knowledge without Knowledge of all the Physical Facts



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 (1990)
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 (1992) distinguishes
*metaphysical physicalism* from *linguistic
physicalism*. While metaphysical physicalism is the ontological
claim that there are no non-physical individuals, properties or
relations and no non-physical facts, linguistic physicalism says that
"everything physical can be expressed or captured in the
languages of the physical sciences." According to Flanagan
Mary's case may refute linguistic physicalism but does not refute
metaphysical physicalism. Alter (1998) 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.


### 4.3 No Propositional Knowledge 1: the Ability Hypothesis



Two different versions of the *No Propositional Knowledge*-View
have been proposed. According to the *Ability Hypothesis* (most
prominently defended in Lewis 1983, 1988 and in Nemirow 1980, 1990,
2007), Mary does not acquire any new propositional knowledge after
release (no knowledge about something that is the case, no factual
knowledge), but only a bundle of abilities (like the ability to
imagine, remember and recognize colors or color experiences).
According to the *Acquaintance Hypothesis* proposed by Conee
(1994), Mary's new knowledge after release is what he calls
"acquaintance knowledge" which is neither propositional
knowledge nor identical to a bundle of abilities.



Proponents of the Ability Hypothesis presuppose that Mary's epistemic
progress after release consists in the acquisition of knowing what it
is like (e.g. to have an experience of blue) and they claim that to
know what it is like *is* to have certain practical abilities.
According to Nemirow "knowing what an experience is like is the
same as knowing how to imagine having the experience" (1990,
495). According to Lewis,



> 
> ...knowing what it is like is the possession of abilities:
> abilities to recognize, abilities to imagine, abilities to predict
> one's behavior by imaginative experiments (Lewis 1983, 131).
> 



A few years later he writes: 



> 
> The Ability Hypothesis says that knowing what an experience is like
> just *is* the possession of these abilities to remember,
> imagine, and recognize. ... It isn't knowing-that. It's
> knowing-how (Lewis 1990, 516).
> 



Bence Nanay suggests that what Mary acquires is the ability to
discriminate between different types of awareness, i.e., to
distinguish having or imagining experiences of type *E* from
having or imagining experiences of other types (2009).



Lewis's main argument for the Ability Hypothesis can be summarized
like this. (1) The only alternative to the Ability Hypothesis is what
he calls the *Hypothesis of Phenomenal Information* (HPI).
(According to the HPI knowing what it is like is propositional in the
following sense: coming to know what it is like involves the
elimination of hitherto open possibilities). (2) The HPI is
incompatible with physicalism. (3) The Ability Hypothesis is
compatible with physicalism and explains everything that may be
explained by the HPI. Therefore: 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:



> 
> ...it would be perverse to claim that bare experience can provide
> us only with practical abilities.... By being shown an unfamiliar
> color, I acquire information about its similarities and
> compatibilities with other colors, and its effects on other mental
> states: surely I seem to be acquiring certain facts about color and
> the visual experience of it (Levin 1986, 246; see also Crane 2003).
> 



But, as pointed out by Tye (2000), this does not undermine the Ability
Hypothesis. The Ability Hypothesis implies that there is some
knowledge that can *only* be acquired by having experiences of
a particular kind and that *this* knowledge is nothing but
knowing-how. This of course does not exclude that there *also*
is *propositional* knowledge that *can* be acquired by
getting acquainted with kinds of experiences from the first person
perspective. The proponent of the Ability Hypothesis only has to
insist that, *if* there is such propositional knowledge, then
it *need not* be acquired on that particular basis but is
accessible in other ways as well.


### 4.4 Objections Against the Ability Hypothesis



It has been argued against Nemirow that the ability to imagine having
an experience of a particular kind is neither necessary nor sufficient
for knowing what it is like to have that kind of experience. To show
that imaginative abilities are not necessary for knowing what it is
like, Conee (1994) and Alter (1998) cite the example of a person who
has no capacity to imagine having color experiences. They claim that
despite this defect she would know what it is like to have an
experience of e.g. green while attentively staring at something that
looks green to her. To show that imaginative abilities are not
sufficient for knowing what it is like Conee introduces the following
example: A person, Martha, "who is highly skilled at visualizing
an intermediate shade that she has not experienced between pairs of
shades that she has experienced...happens not to have any
familiarity with the shade known as cherry red." Martha is told
that cherry red is midway between burgundy red and fire red (she has
experienced the latter two shades of red). Given this information and
her extraordinary capacity, Martha has the ability to imagine cherry
red, but as long as she does not *exercise* this ability she
does not know what it is like to see cherry red.



A similar example is used for the same purpose and discussed in more
detail by Raymont 1999. Raymont argues that mnemic, recognitional and
imaginative abilities neither separately nor conjointly amount to
knowing of what it is like to have a particular kind of experience. He
first argues that none of these abilities is necessary and sufficient
for knowing what it is like: (a) Mnemic abilities are not necessary,
since someone can learn what an experience is like when first having
it without already remembering an experience of the relevant kind. (b)
Imaginative abilities are not sufficient since someone can have the
ability to imagine a particular kind of experience without exercising
it (see the example cited above). (c) To show that recognitional
abilities are not sufficient either, Raymont cites empirical data
"in support of the view that one can have the ability to
noninferentially recognize a certain type of visual experience without
ever having had it, and thus without knowing what it is like to have
it". But then these three kinds of abilities cannot conjointly
amount to knowing what it is like either: if they did,
then - contrary to (a) - each of them would have to be a
necessary condition for knowing what it is like.



Gertler (1999) argues that the best candidate for an analysis in the
spirit of the Ability Hypothesis is to identify knowing what it is
like to have an experience of red with the ability to recognize
seeing-red experiences by their phenomenal quality and then goes on to
attack this candidate: she points out that the ability to recognize
seeing-red experiences by their phenomenal quality can be explained by
the fact that I know what it is like to see red but not *vice
 versa*.[3]



Michael Tye (2000) concedes that none of the abilities considered by
Lewis is necessary for knowing what it is like and he discusses the
following possible revision of the Ability Hypothesis: knowing what it
is like to have an experience of red is the ability to apply an
indexical concept to an experience of red (while having it) via
introspection. But, he goes on to argue, this revised version can
again be rejected by a counterexample that shows that the ability at
issue is not sufficient for knowing what it is like: If Mary is
distracted and does not attend to her experience when she first sees a
red object, then she need not apply any concept to her experience at
all. In this case, she still does not know what it is like to have red
experiences although she has the *ability* to apply an
indexical concept to her present experience (she has the ability, but,
being distracted, she does not exercise it). Tye concedes that the
revised version of the Ability Hypothesis could not, anyway, be used
against the knowledge argument in the way that was originally
intended. The reason is that the revised version is compatible with
the view that Mary does acquire knowing-that if she is not distracted
when first seeing something red: she learns that *this* is a
red experience (where "this" refers introspectively to her
present experience) and so acquires knowing-that. According to Tye to
have indexical knowledge of this kind is sufficient but not necessary
for knowing what it is like to have a red experience. After all, it is
impossible to introspectively refer to a red experience without
presently having that kind of experience, but Tye wishes to concede
that a person can know what it is like to have a red experience while
not presently having a red experience. This reasoning motivates his
disjunctive account of knowing what it is like: "*S*
knows what it is like to undergo experience *E* iff either
*S* now has indexical knowledge-that with respect to *E*
obtained via current introspection or *S* has the Lewis
abilities with respect to *E*" (Tye 2000). Tye thus
defends the physicalist view against the knowledge argument by a
combination of the two strategies mentioned above: he applies the
*New Knowledge/Old Fact*-strategy to the person who knows what
it is like to have an experience in the sense of the first conjunct
(the indexical thought at issue is made true by a physical fact) and
he applies the *No Propositional Knowledge*-strategy to the
case of someone who has knowing what it is like in the sense of the
second disjunct.



Lycan (1996) argues against the Ability Hypothesis and for the view
that Mary acquires new knowledge-that after release by claiming that
"*S* knows what it is like to see blue" means
something like "*S* knows that it is like *Q* to
see blue" where *Q* names the phenomenal quality at
issue. It has been objected by Tye (1995) that the use of the qualia
name "*Q*" within a propositional attitude context
creates the well-known problems: Replacing "*Q*" by
another name "*R*" for the same quale may change
the truth value of the belief ascription. A proponent of Lycan's view
could however respond along the following lines: In the case of qualia
names within belief contexts it does not matter which name is used to
refer to the quale at issue as long as the belief is meant in the
sense of a phenomenal belief ascription. "*S* believes
that it is like *Q* to see blue" means, on the phenomenal
reading, that *S* has the relevant belief about *Q*
under a phenomenal concept of *Q*. Under the assumption that it
is impossible to have two different phenomenal concepts of one and the
same quale, the objection is met: As long as two qualia names
*Q* and *R* refer to the same quale, replacing
*Q* by *R* in an ascription of phenomenal belief cannot
change the truth value of the belief ascription.



As we have seen, proponents of the Ability Hypothesis assume that the
know-how which Mary acquires is distinct from any propositional
knowledge. This assumption can be challenged, based for example on the
work of Jason Stanley and Timothy Williamson (2001). On this view, for
a subject *S* to know how to do something (to F) is for
*S* to know that there is a way *w* for *S* to F,
and for *S* to know this under a practical mode of presentation
(2001, 430). Stanley & Williamson themselves apply this thought to
Lewis's version of the Ability Hypothesis:



> 
> Knowing how to imagine red and knowing how to recognize red are both
> examples of knowledge-that. For example, *x*'s knowing how to
> imagine red amounts to knowing a proposition of the form
> '*w* is a way for *x* to imagine red',
> entertained under a guise involving a practical mode of presentation
> of a way (2001, 442; see also McConnell 1994).
> 



Yuri Cath suggests that this point can be accommodated by proponents
of the Ability Hypothesis, provided they distinguish between Mary's
learning a new proposition and her coming to be in new state of
propositional knowledge (2009, 142-143). Specifically, before
her release Mary can know that *w* is a way for someone to
imagine red, but only under a theoretical mode of presentation; after
her release, she comes to know the same proposition under a practical
mode of presentation. She thus comes to be in a new state of
propositional knowledge, but without learning any new
 propositions.[4]


### 4.5 No Propositional Knowledge 2: The Acquaintance Hypothesis



Earl Conee (1994) proposes another variant of the *No Propositional
Knowledge*-View. According to Conee acquaintance constitutes a
third category of knowledge that is neither reducible to factual
knowledge nor to knowing-how and he argues that Mary acquires after
release only acquaintance knowledge. According to Conee knowing
something by acquaintance "requires the person to be familiar
with the known entity in the most direct way that it is possible for a
person to be aware of that thing" (1994, 144). Since
"experiencing a quality is the most direct way to apprehend a
quality" (Conee 1994, 144), Mary gains acquaintance with color
qualia only after release. According to the view proposed by Conee the
physicalist can defend himself against the knowledge argument in the
following way: (1) Qualia are physical properties of experiences (and
experiences are physical processes). Let *Q* be such a
property. (2) Mary can know all about *Q* and she can know that
a given experience has *Q* before release,
although - before release - she is not acquainted with
*Q*. (3) After release Mary gets acquainted with *Q*,
but she does not acquire any new item of propositional knowledge by
getting acquainted with *Q* (in particular she already knew
under what conditions normal perceivers have experiences with the
property *Q*). More recently Michael Tye (2009, 131-137)
defends the acquaintance hypothesis as the right answer to the
knowledge argument thereby abandoning his original response (see below
4.7).



A friend of the knowledge argument might concede that a person is
acquainted with *Q* only if she has or had an experience with
property *Q* but he would have to insist that being acquainted
with *Q* in that sense is a necessary condition for being able
to know (in the relevant sense) that an experience has *Q*.
Another kind of criticism of the Acquaintance Hypothesis is developed
in Gertler (1999). She argues that the property dualist can explain
why the most direct way to get familiar with a quale is by having an
experience of the relevant kind while the physicalist does not have
any explanation for this particular feature of qualia. Similarly,
Robert Howell (2007, 146) argues that all other physicalist responses
to the Knowledge Argument depend upon the Acquaintance Hypothesis, and
that acquaintance is incompatible with objectivism (see Section 4.9
below).



It is interesting to see that one version of the New Knowledge/Old
Fact View is very similar in spirit to the Acquaintance Hypothesis.
Bigelow and Pargetter (1990) argue that Mary's progress after release
consists in the fact that she now stands in a new acquaintance
relation to color qualia, but their theory about the individuation of
beliefs implies that she thereby acquires new factual knowledge.
Different beliefs, according to Bigelow and Pargetter, can be
distinguished appropriately only if one takes into consideration the
way the subject is acquainted with the individuals and properties her
belief is about (they use the technical term "modes of
acquaintance" in that context).


### 4.6 The New Knowledge/Old Fact View



Several positive arguments for the view that Mary's new knowledge
after release constitutes propositional knowledge (genuine
information) have been formulated in the literature. Lycan argues, for
example, that Mary's new knowledge goes along with the elimination of
epistemic possibilities and that her new abilities are best explained
by her having new information (for further arguments see Lycan 1996,
92). Loar (1990/1997) points out that the embedded occurrence of
"feels like such and such" in sentences like
"*if* pains feel like such and such then
*Q*" cannot be accounted for in a model that treats
knowing what it is like as mere know-how. McConnell (1994) defends the
more radical view that the acquisition of knowing-how is normally
accompanied by the acquisition of a particular new item of
knowing-that.



Many philosophers find it hard to deny that Mary gains new factual
knowledge after release and for that reason (if they are physicalists)
feel attracted by the New Knowledge/Old Fact View. Positions that
clearly fall into that category are defended in Horgan 1984;
Churchland 1985; Tye 1986, 1995; Bigelow and Pargetter 1990; Loar
1990/1997; Lycan 1990a, 1996; Pereboom 1994; Perry 2001; Byrne 2002;
Papineau 2002, 2007; Van Gulick 2004; Levin 2007; Balog 2012a,
2012b.



The basic ideas common to the New Knowledge/Old Fact View may be
summarized as follows:



> 
> (1) Phenomenal character, e.g. phenomenal blueness, is a *physical
> property* of experiences (but see Lycan 1990a for an exception who
> construes qualia as properties of external objects).
> 
> 
> (2) To gain knowledge of what it is like to have an experience of a
> particular phenomenal character requires the acquisition of
> *phenomenal concepts* of phenomenal
>  character.[5]
> 
> 
> 
> (3) What it is for an organism to acquire and possess a phenomenal
> concept can be fully described in broadly physical terms.
> 
> 
> 
> (4) A subject can acquire and possess phenomenal concepts only if it
> has or has had experiences of the relevant phenomenal kind.
> 
> 
> 
> (5) After release Mary gains knowledge about phenomenal characters
> under phenomenal concepts.
> 
> 
> 



But the facts that make these new items of knowledge true are physical
facts that Mary knew before release under another
conceptualization.



The differences between variants of the New Knowledge/Old Fact View
concern the theoretical (physicalist) account of (a) phenomenal
character, (b) phenomenal concepts of phenomenal characters and (c)
the relation between phenomenal characters and the corresponding
phenomenal concepts. All proponents of the view point out that,
according to their proposal, physical concepts and phenomenal concepts
are cognitively independent: it is impossible to see *a priori*
that something that falls under a *physical concept* of a
particular phenomenal character also falls under the corresponding
*phenomenal concept* of that phenomenal character. This is why
it is possible to have (like Mary) complete physical knowledge about
e.g. phenomenal blueness (you know everything there is to know about
phenomenal blueness under its physical conceptualization) without
having a phenomenal concept of blueness and without knowing any of
these facts under a phenomenal concept of blueness. Some have argued
that the phenomenal conceptualization is not expressible in language
(see Byrne 2002 and Hellie 2004).



In general, if a philosopher *A* claims that the argument of
philosopher *B* does not go through, it is a point in favor of
his view if he can provide an error theory, that is if he can explain
why the argument may *appear* correct in the first place. The
New Knowledge/Old Fact View can claim to have an error theory with
respect to the knowledge argument. Given the cognitive independence of
physical and phenomenal concepts of blueness it *appears as if*
we could imagine a situation where everything Mary knew before release
were fulfilled but not what she came to know after release (and this
can be taken to imply that she *does* come to know new facts).
But, according to the New Knowledge/Old Fact View this is an illusion.
There is no such possible situation. What Mary learns after release is
made true by a physical fact that she already knew before her release.
Some versions of the New Knowledge/Old Fact-View will be briefly
described in what follows.


### 4.7 Variants of the New Knowledge/Old Fact View



Horgan (1984) does not provide a developed theoretical account of
phenomenal concepts but is one of the first to formulate the basic
intuition shared by most or all proponents of the New Knowledge/Old
Fact View: By having experiences of blue, Mary gets acquainted with
phenomenal blueness (which is in fact a physical property of
experiences) "from the experiential perspective," she
gains what he calls "the first person ostensive perspective on
that property" (Horgan 1984, 151): she now can refer to
phenomenal blueness by thinking or saying "*that* kind of
property" while having, remembering or imagining a blue
experience and while attending to its particular quality. She thus has
acquired a new *concept* of phenomenal blueness. Using this new
concept she can form new beliefs (and acquire new knowledge) about
phenomenal blueness. Formulated in this way, the view may appear
similar to Conee's acquaintance account. According to both views,
Mary's progress consists primarily in getting acquainted with
phenomenal blueness from an inner perspective. But contrary to Conee's
thesis, according to the New Knowledge/Old Fact View, acquaintance
with phenomenal blueness from an experiential perspective enables the
subject to form a *new concept* of phenomenal blueness and
thereby implies the capacity to acquire *new beliefs*.



An example of a more explicit theoretical account of phenomenal
character, phenomenal content and their relation can be found in Tye
(1995). He proposes a representationalist account of phenomenal
character. For a state to have phenomenal character is to represent
internal or external physical items in an 'abstract' and
nonconceptual way that is "appropriately poised for use by the
cognitive system" (see Tye 1995, 137-144). According to
Tye, there are two kinds of phenomenal concepts: indexical concepts
(an example is the concept applied when thinking of a particular shade
of red as "this particular hue" while having a red
experience) and what he calls "predicative phenomenal
concepts" that are based on the capacity to make certain
discriminations. Tye wishes to accommodate the natural intuition that
Mary before release cannot fully understand the nature of phenomenal
blueness (she doesn't really know what it is to have a blue
experience). One might think that his view is incompatible with the
intuition at issue. Phenomenal blueness, according to his view, has a
physical nature and one might expect that physical natures are fully
describable in physical terms and fully understandable under a
physical conceptualization. But Tye has a surprising response:
although phenomenal blueness has a physical nature, a person cannot
fully understand its nature unless she thinks of phenomenal blueness
under a phenomenal concept.



Another representationalist view about phenomenal character is
combined with the New Knowledge/Old Fact View in Lycan (1990a) and
(1996). Lycan's account of Mary's epistemic progress can be put,
roughly, like this: Only after release Mary can form
"introspective second order representations" of her own
color experiences. One may think of an introspective representation as
of "a token in one of the subject's languages of thought, his or
her Introspectorese". It has often been said that what Mary
learns is in some sense "ineffable", that it cannot be
communicated in public language. Lycan is led to a similar conclusion
within his computational theory. In his view, when Mary finally has an
experience of blue she "tokens a semantically primitive mental
word for the type of first-order state being inwardly sensed",
where this word in Mary's language of thought has an
"inferential and/or conceptual role" that is "unique
to its subject, in that no other subject could deploy a functionally
similar representation whose designatum was that (the subject's) very
same first-order state-token, ...." And he concludes that
"the introspective word would certainly not be synonymous with
any primitive or composite expression of public
English,..." (Lycan 1996, 101).



Papineau (1996) distinguishes third person and first person thoughts
about experiences. First person thoughts involve the imagination of an
experience of the relevant kind. The basic idea may be put like this:
When Mary is finally released and after some time sufficiently
acquainted with color experiences she can 'reproduce' blue
experiences in her imagination. These imaginations of experiences of a
particular kind can be used to refer to experiences of the kind at
issue and to think about them. Obviously, Mary could not have first
person thoughts about color experiences (she could not use imagined
blue experiences in order to refer and to think about blue
experiences) before she ever had blue experiences. After release, Mary
can acquire new beliefs: first person beliefs about blue experiences.
But for every such new *first* person belief about a given kind
of experience, there will be one of her old *third* person
beliefs which refers to the same kind of experience and has the same
factual content.



Another way to understand phenomenal concepts is as a species of
indexical concepts. For instance, Perry (2001) argues that Mary's new
knowledge after release does not pose a problem to physicalism any
more than indexical thoughts like "I am a philosopher" or
"today is Sunday" (for a defense of this claim see also
McMullen 1985). Perry treats Mary's new knowledge as a particular case
of demonstrative belief (and he proposes an account of Mary's new
beliefs after release in terms of his theory of token-reflexive
thoughts). After release, when seeing the sky, Mary may think
"Oh, so having blue experiences is like *this*"
where "this" refers to a physical property (the phenomenal
character) of her present color experience. She could not have had a
demonstrative belief of this kind before release. But, again, the fact
that makes the thought true is simply the fact that blue experiences
have the particular physical property at issue. Therefore, she does
not learn any new fact.



Doubts about Perry's proposal have been raised along the following
lines. In normal cases of demonstrative reference the demonstrated
object is in some way given to the epistemic subject (when pointing to
a table and referring to it by "this table", the object
may be given as "the next table left to me"). But what is
the way the kind of experience is given to Mary when she thinks of
phenomenal blueness under the demonstrative concept "this kind
of experience?" It cannot be the way it feels to have an
experience with that property, since this solution, so one may argue,
introduces phenomenal characters of phenomenal characters and thus
reintroduces the original problem. Maybe "the kind of experience
I am now having" is the appropriate candidate. But there are
problems with this proposal too (see Chalmers 2002). There are also
problems with suggesting that the demonstrative concept is
'thin', in the sense that it has no reference-fixing mode
of presentation associated with it (for some of these problems see
Demircioglu 2013, 263-269).



Robert Stalnaker (2008) raises further doubts regarding Perry's
treatment of Mary's new knowledge. Drawing on a distinction between
the two stages of Mary's epistemic progress (see Section 3.3 above),
he argues that the cases of acquiring demonstrative beliefs which
Perry compares with Mary's new knowledge are akin to the second
stage of Mary's progress, but "It is at stage one that the
problematic cognitive achievement - the learning 'what
it is like' to see red - takes place" (2008,
44).



Stalnaker suggests an alternative way in which Mary's new knowledge
is demonstrative in character. On this proposal, what Mary acquires is
essentially contextual information, where "the content of what
is expressed or believed in a context is not detachable from the
context in which it is expressed or believed" (2008, 81). As an
example of such information, Stalnaker describes a bomb disposal
expert pointing at the ground and saying "A bomb is buried
there, and unless we defuse it now it will explode within five
minutes" (2008, 85). This information, Stalnaker suggests,
cannot be known by someone who was not in that situation at that time,
even if they know the exact co-ordinates of where the bomb is located
and when it will detonate. Daniel Stoljar (2011) argues that
phenomenal knowledge is not essentially contextual. In defence of this
claim, he suggests there is an important dis-analogy between the
difference between Mary, pre- and post-release, and the difference
between the bomb disposal expert and anyone who was not with her when
she made her utterance. The thought which the bomb disposal expert
expressed in her utterance could not even be entertained by someone
who was not present at that time; it is for this reason that someone
not there could not know what the expert knew. In contrast, Stoljar
suggests that "the fact that post-release Mary learnt could have
been entertained by pre-release Mary (e.g., she can wonder whether it
obtains)" (2011, 441). This suggests that what Mary learns upon
release is not essentially contextual, at least not in the sense which
Stalnaker has in mind.



Another worry about demonstrative accounts is that they do not seem to
do duty to the way in which the subjective character itself is present
to the mind of the thinker when employing a phenomenal concept of that
character. This worry is sometimes put in terms of acquaintance: the
specific way in which the thinker is acquainted with the referent of
her thought in using phenomenal concepts does not seem to be captured
by the demonstrative account (see Levine 2007; Howell 2007,
164-166). Several attempts have been made to answer objections
of this kind. Papineau (2002) and Balog (2012a) argue that the
cognitive intimacy to be accounted for is well explained by a
quotational theory of phenomenal concepts: in thoughts involving
phenomenal concepts token experiences are used in order to refer to
the kind those tokens belong to. Levine (2007) argues that even these
refined theories do not account for the specific intimate way in which
the thinker is related to the referents of phenomenal concepts.
Contrary to this Levin (2007) does not see any need to
'embellish' the original simple demonstrative account.
While Balog's current position is an elaborated version of the
quotational account, Papineau has abandoned the quotational theory and
argues in Papineau (2007) that phenomenal concepts are special cases
of perceptual concepts where perceptual concepts do not involve
demonstration.



An influential view about phenomenal concepts which answers the
knowledge argument admitting that Mary gains new knowledge but no
knowledge of new facts is developed in Loar (1990/1997): Phenomenal
concepts are recognitional concepts. To have the phenomenal concept of
blueness is to be able to recognize experiences of blueness while
having them. The recognitional concept of blueness refers
*directly* to its referent (the physical property of blueness)
where this means (in Loar's terminology): there is no other
property (no property of that property) involved in the reference
fixing. According to Loar's view the recognitional concept of
phenomenal blueness refers to the physical property phenomenal
blueness in virtue of being 'triggered' by that
property. It has been doubted that 'directness' in
Loar's sense provides an account for what one might call
acquaintance: for the way in which the phenomenal character is present
to the mind when a thinker employs phenomenal concepts (see Levine
2007). White (2007) argues against Loar that the account cannot
explain the a posteriori character of mind-brain identity statements
in a satisfying manner.


### 4.8. Objections Against the New Knowledge/Old Fact View



An objection to the New Knowledge/Old Fact View can be made as
follows. In standard cases, if a subject does not know a given fact in
one way that it does know in some other way, this can be explained by
two modes of presentation: the subject knows the fact under one mode
of presentation and does not know it under some other mode of
presentation. So, for example, a person may know the fact that Venus
is a planet under the mode of presentation associated with "the
morning star is a planet" and fail to know the very same fact
under the mode of presentation associated with "the evening star
is a planet." In this particular case, as in many others, the
difference in the mode of presentation involves two different
properties that are used to fix the referent. In one mode of
presentation Venus is given as the heavenly body visible late in the
morning (or some similar property), whereas in the other mode of
presentation the object is given as the heavenly body visible early in
the evening.



If the New Knowledge/Old Fact View involves two modes of presentation
of this sort, then it cannot be used to defend physicalism because
this kind of explanation of the supposed double epistemic access to
facts concerning phenomenal types would reintroduce non-physical
properties at a higher level: the subject would have to be described
as referring to the phenomenal type at issue by some physical property
in case it believes the relevant fact under its physical mode of
presentation and as referring to that phenomenal type by some
non-physical property in case it believes the relevant fact under its
phenomenal mode of presentation.



It has been argued by several authors that the different modes of
presentation at issue in the case of beliefs about phenomenal states
do involve the introduction of different reference-fixing properties
and that therefore the proposal is unsuccessful. Arguments of that
kind are found in Lockwood (1989, chap. 8) and McConnell (1994). White
(2007) develops the objection in detail. Block (2007) gives a detailed
answer to White (2007) based on a distinction between what he labels
cognitive and metaphysical modes of presentation. Chalmers (1996,
2002, 2010) makes a similar point as White (2007) using his framework
of primary and secondary intensions. In that framework, primary
intensions describe the way a concept picks out its referent in the
actual world and the cognitive independence of phenomenal and physical
concepts is explained by their different primary intensions. If one
singular fact can be known under a physical mode of presentation as
well as under a phenomenal mode of presentation, then the two items of
knowledge involve two concepts (a phenomenal and a physical concept)
with different primary intensions and these different primary
intensions correspond to different properties.



A two-dimensional framework is used in a different manner in
Nida-Rumelin (2007) to develop the idea that the nature of
phenomenal properties is present to the mind of the thinker when using
phenomenal properties - an idea which leads to the result that the
New Knowledge/Old Fact View is mistaken. This idea is also suggested
by Philip Goff (2017). He suggests that the knowledge argument does
not by itself refute physicalism because it does not overcome the New
Knowledge/Old Fact View. However, things are different if the
phenomenal concept which Mary acquires is *transparent* (i.e.,
it reveals the nature or essence of the phenomenal property which
satisfies it):



> 
> in this case Mary's new knowledge is knowledge of the nature of red
> experiences, but if pure physicalism is true, she already knew the
> complete nature of red experiences in knowing the pure physical
> truths, and hence there ought to be nothing more she can learn about
> their nature (2017, 74-75; see also Furst 2011,
> 69-70; Demircioglu 2013, 274-275).
> 



A general argument against the materialist strategy of appealing to
phenomenal concepts is developed in Chalmers (2004; 2007); for
critical discussion see Balog (2012b). 



Anyone who wishes to argue in the way just mentioned, that the two
modes of presentation do involve the introduction of two different
reference-fixing properties, must deal with Loar's proposal (see 4.7).
Loar avoids the problem of two reference fixing properties by his
claim that phenomenal concepts refer directly to their referent. It
has been argued against Loar that his causal account of how phenomenal
concepts manage to directly refer to their referent (namely by being
triggered by them) cannot appropriately describe the particular
cognitive role of phenomenal concepts (see McConnell 1994 and White
2007).



A final issue concerning both the New Knowledge/Old Facts View and the
knowledge argument itself is whether there are any phenomenal
concepts. Derek Ball (2009) and Michael Tye (2009) argue that there
are no such concepts, at least as defined above: in particular, both
deny claim (4) outlined in Section 4.6, that a subject can possess
phenomenal concepts only if it has or has had experiences of the
relevant kind. Ball and Tye appeal to work on social externalism
regarding the content of our concepts to argue that even prior to her
release, Mary possesses the same concepts which she uses to think
about her experiences after her release. Specifically, she possesses
such concepts 'deferentially', in virtue of interacting
with her linguistic community; a crucial part of social externalism
about content is that one can possess concepts deferentially even
though one is largely ignorant of the nature of what satisfies these
concepts (Ball 2009, 947-954; Tye 2009,
 63-70).[6]
 This result threatens to undermine the New Knowledge / Old Facts
View, but Ball suggests it also undermines the knowledge argument
itself, since the knowledge argument itself depends on there being
phenomenal concepts (2009, 940-943).



Torin Alter (2013) responds to these arguments by focusing on the
distinction between deferential and non-deferential concept possession
(the latter is *conceptual mastery*). He suggests that it is
mastery of phenomenal concepts rather than mere deferential possession
which matters for the knowledge argument: "Mary makes epistemic
progress when she leaves the room because she comes to master or
non-deferentially possess phenomenal colour concepts" (2013,
486). And defenders of the knowledge argument can claim that mastery
of a phenomenal concept requires actually having experiences with the
relevant phenomenal character.


### 4.9 The Knowledge Argument and Objectivism



The Knowledge Argument has traditionally been understood as an
argument against physicalism or perhaps against reductive versions of
physicalism. But an influential alternative approach sees the argument
as working not against physicalism per se, but against a different
position which can be termed
 *objectivism*.[7]
 Objectivism is the view that an objective description of what exists
can be complete; that there are no aspects of reality which can only
be understood by having experiences of a specific type. This notion is
closely related to Nagel's characterization of the physical nature
of organisms as "a domain of objective facts *par
excellence* - the kind that can be observed and understood
from many points of view and by individuals with differing perceptual
systems" (1974, 442). On this view, the point of Jackson's
thought experiment is to bring out that Mary learns something which
can only be known by having an experience of a certain kind (e.g., a
perceptual experience). If this is correct, then this shows that no
objective description of what exist can be complete. As Howell
formulates it, the argument understood in this way runs as
follows:



> 
> before leaving the room, Mary knew all the objective information about
> the world. When she left the room, she gained further understanding
> about the world. Therefore, all the objective information about the
> world is insufficient for a complete understanding of the world (2007,
> 147).
> 



A number of proponents of this interpretation of the Knowledge
Argument suggest that it is compatible with a specific form of
physicalism, on which all facts are physical or metaphysically
necessitated by microphysical facts but some facts can only be
understood by having specific experiences (see, e.g., Kallestrup 2006;
Howell 2007; for slightly different formulations see Crane 2003; Zhao
2012). That said, it is worth asking how the 'physical' is
to be understood, such that facts which can only be known if one has
certain experiences can count as physical. Furthermore, it is worth
questioning whether a view on which facts are either physical or
metaphysically necessitated by microphysical facts thereby counts as a
form of physicalism. It has been argued that such a view is compatible
with non-physicalist positions such as emergentism or certain forms of
ethical non-naturalism (see Horgan 1993, 559-566; 2010, 311-314; Crane
2010; for discussion see Stoljar 2017, section 9).


## 5. The Dualist View About the Knowledge Argument



There has not been much discussion of the knowledge argument from a
dualist perspective. This is unsurprising given the small number of
contemporary philosophers who defend a dualist position (for a
prominent exception see Chalmers (1996); the knowledge argument is
discussed on pp. 140-146). There are two possible strategies for
a dualist to take who wishes to defend the knowledge argument. The
first is merely defensive or 'destructive' in that it
tries to refute the positive theoretical proposals one by one that
have been used by physicalists in their objections against the
knowledge argument. The second is more 'constructive' in
that it aims at developing an alternative positive dualist account of
phenomenal concepts, phenomenal properties and their relations such
that on that account Mary does learn new and nonphysical facts upon
release. Examples (or partial examples) for the first strategy may
occasionally be found in the literature (compare Warner 1986, Gertler
1999, Raymont 1995, 1999 and Connell 1994). Examples for the second
are hard to find, but Chalmers (1996, 2002) and Nida-Rumelin
(2007) exemplify the second strategy. Using his framework of primary
and secondary intensions he develops a positive account of what he
calls "pure phenomenal concepts" that can be described as
incorporating the old and natural intuition that in the case of qualia
(phenomenal characters) there is no distinction between appearance and
reality, in other words: qualia 'reveal their nature' in
experience.



The intuitive idea just mentioned has been expressed in different
ways. Some say that qualia 'have no hidden sides'. Others
say that qualia are not natural kind terms in that it is *not*
up to the sciences to tell us what having an experience of a
particular kind amounts to (we know what it amounts to by having them
and attending to the quality at issue). It is quite clear that an
account of this intuitive idea has to be one of the ingredients of a
dualist defense of the knowledge argument. Nida-Rumelin (2007)
develops a technical notion of grasping properties which is intended
to serve the purposes of dualists who argue against materialism using
the assumption that in the special case of phenomenal concepts the
relation that the thinker bears to the property he conceptualizes is
more intimate than in other cases: the thinker understands what having
the property essentially consists in. This idea can be used to block
familiar objections to the knowledge argument in particular those
falling into the Old fact/ New Knowledge category. A similar basic
idea but formulated within a different theoretical framework is
elaborated in Stephen White (2007). 



According to mainstream opinion the most serious problem for property
dualism is the danger of being driven into epiphenomenalism. If
phenomenal characters are non-physical properties and if every
physical event has a physical cause and if we exclude the possibility
of overdetermination (where something is caused by two different
causes that are both sufficient), then, arguably, whether or not a
state has a particular phenomenal character cannot have any causal
relevance. But if qualia are causally impotent, how can a person know
that she has an experience with a particular phenomenal character?
Many take it to be obvious that a person cannot know that she now has
a blue experience unless her blue experience plays a prominent causal
role in the formation of her belief at issue. This particular problem
has been formulated as an objection against the knowledge argument in
Watkins (1989). Until some time ago Jackson was one of the very few
philosophers who embraced epiphenomenalism. But Jackson changed his
mind. Jackson (1995) argues that knowledge about qualia is impossible
if qualia are epiphenomenal and he concludes that something must be
wrong with the knowledge argument. In Jackson (2003) and Jackson
(2007) he argues that the argument goes wrong in presupposing a false
view about sensory experience and that it can be answered by endorsing
strong representationalism: the view that to be in a phenomenal state
is to represent objective properties where the properties represented
as well as the representing itself can be given a physicalist account.
Jackson admits that there is a specific phenomenal way of representing
but he now insists that the phenomenal way of representing can be
accounted for in physicalist terms. Doubts about the latter claim are
developed in Alter (2007). Other possible reactions to the threat of
epiphenomenalism for dualism would be either to doubt that a property
dualist must embrace epiphenomenalism or to develop an account of
knowledge about one's own phenomenal states that does not imply a
causal relation between qualia and phenomenal knowledge about qualia
(see Chalmers 2002).


## 6. Concluding Remark



The appropriate evaluation of the knowledge argument remains
controversial. The acceptability of its second premise P2 (Mary lacks
factual knowledge before release) and of the inferences from P1 (Mary
has complete physical knowledge before release) to C1 (Mary knows all
the physical facts) and from P2 to C2 (Mary does not know some facts
before release) depend on quite technical and controversial issues
about (a) the appropriate theory of property concepts and their
relation to the properties they express and (b) the appropriate theory
of belief content. It is therefore safe to predict that the discussion
about the knowledge argument will not come to an end in the near
future.