the doctrine that the world is entirely physical. The argument begins
with the claim that there are truths about consciousness that cannot
be deduced from the complete physical truth. For example, Frank
Jackson's Mary, learns all the physical truths from within a
black-and-white room. Then she leaves the room, sees a red tomato for
the first time, and learns new truths—new phenomenal truths about what
it's like to see red. The argument then infers that, contrary to
physicalism, the complete physical truth is not the whole truth. The
physical truth does not determine or metaphysically necessitate the
whole truth about the world.
This article discusses the argument's structure, compares Jackson's
version with others, compares the knowledge argument with other
anti-physicalist arguments, and summarizes the main lines of response.
Eight controversial assumptions are identified. These are the
assumptions that:
* the notion of the physical is coherent;
* the complete physical truth is accessible to the pre-release Mary;
* upon leaving the room, she learns something;
* the kind of knowledge she acquires upon leaving the room is
informational knowledge, rather than ability knowledge, acquaintance
knowledge, or something else;
* she gains new information, rather than old information
represented in a new way;
* if the complete-knowledge claim and the learning claim are true,
then what Mary learns when she leaves the room cannot be a priori
deduced (deduced by reason alone, without empirical investigation)
from the complete physical truth.
* if there are phenomenal truths that cannot be a priori deduced
from the complete physical truth, then the complete physical truth
does not metaphysically necessitate those phenomenal truths;
* the knowledge argument and epiphenomenalism are consistent.
Various criticisms and defenses of these assumptions are discussed.
1. Introduction
The knowledge argument aims to refute physicalism, the doctrine that
the world is entirely physical. Physicalism (also known as
materialism) is widely accepted in contemporary philosophy. But some
doubt that phenomenal consciousness—experience, the subjective aspect
of the mind—is physical. The knowledge argument articulates one of the
main forms this doubt has taken.
Frank Jackson gives the argument its classic statement (in Jackson
1982 and Jackson 1986). He formulates the argument in terms of Mary,
the super-scientist. Her story takes place in the future, when all
physical facts have been discovered. These include "everything in
completed physics, chemistry, and neurophysiology, and all there is to
know about the causal and relational facts consequent upon all this,
including of course functional roles" (Jackson 1982, p. 51). She
learns all this by watching lectures on a monochromatic television
monitor. But she spends her life in a black-and-white room and has no
color experiences. Then she leaves the room and sees colors for the
first time. Based on this case, Jackson argues roughly as follows. If
physicalism were true, then Mary would know everything about human
color vision before leaving the room. But intuitively, it would seem
that she learns something new when she leaves. She learns what it's
like to see colors, that is, she learns about qualia, the properties
that characterize what it's like. Her new phenomenal knowledge
includes knowledge of truths. Therefore, physicalism is false.
In the late 1990's, Jackson changed his mind: he now defends
physicalism and rejects the knowledge argument. But others defend the
argument, and even those who reject it often disagree about where it
goes awry. The knowledge argument has inspired a voluminous
literature, which contains insights about consciousness, knowledge,
the limits of third-person science, and the nature of the physical. It
is also discussed in non philosophical works, including a book by E.
O. Wilson (1998), a work of fiction (Lodge 2001), and a T.V. series
(Brainspotting). This article discusses the argument's structure,
compares Jackson's version with others, compares the knowledge
argument with other anti-physicalist arguments, and summarizes the
main lines of response.
2. The Knowledge Intuition and the Inference to Physicalism's Falsity
The knowledge argument has two parts. One says that physical knowledge
is not sufficient for phenomenal knowledge. Call this the knowledge
intuition (Stoljar and Nagasawa, 2004). The other says that the
knowledge intuition entails the falsity of physicalism.
Thus described, the knowledge argument is not new with Jackson. Locke
and other 18th Century British empiricists discussed the knowledge
intuition. C. D. Broad gave a version of the knowledge argument in
1925. And other versions appear in more recent writings, such as
Thomas Nagel's 1974 "What is it Like to be a Bat?" What is distinctive
about Jackson's contribution?
Daniel Stoljar and Yujin Nagasawa (2004) answer this question in their
introduction to a volume of essays on the knowledge argument. As they
say, Jackson contributes at least two main ideas: his Mary example
illustrates the knowledge intuition better than previous attempts; and
he provides distinctive reasons for inferring physicalism's falsity
from the intuition. Let us take these points in order.
The Mary case divides the knowledge intuition into three claims:
* The complete-knowledge claim: before leaving the room, Mary
knows everything physical.
* The learning claim: upon leaving, she learns something.
* The non-deducibility claim: if the complete-knowledge claim and
the learning claim are true, then what Mary learns when she leaves the
room cannot be a priori deduced (deduced by reason alone, without
empirical investigation) from the complete physical truth.
Physicalists may deny the knowledge intuition. But the Mary case
suggests that doing so requires rejecting the complete-knowledge
claim, the learning claim, or the non-deducibility claim.
The cases discussed by Broad, Nagel, and others do not deliver this
result. Consider, for example, Broad's "mathematical archangel," a
logically omniscient creature who knows all the physical truths about
various chemical compounds. Broad calls these truths "mechanistic"
instead of "physical," but the point is the same. On his view, the
archangel would know all such truths but still lack phenomenal
knowledge concerning, for example, "the peculiar smell of ammonia."
And Broad infers that physicalism ("mechanism") is false. But what if
the physicalist denies that the archangel would lack the relevant
phenomenal knowledge? We appear to be at an impasse. By contrast, if
the physicalist claims that, while in the room, Mary knows what it's
like to see colors, he must explain why she seems to acquire this
knowledge when she leaves. The Mary case breaks the deadlock in favor
of the knowledge intuition. Other illustrations of the intuition that
precede Jackson's have further drawbacks. For example, Nagel's claim
that humans cannot imagine what it's like to be a bat raises
distracting issues about the limits of human imagination, about which
physicalism carries no obvious commitments. Mary's fame is just.
To explain the second of Jackson's distinctive contributions, it will
be useful to explain some terminology and abbreviations. First, there
is the distinction between the a priori and the a posteriori. A priori
truths are those that are justifiable by reason alone, without
empirical investigation. Logical truths provide clear examples. For
example, one can figure out without empirical investigation that the
following claim is true: if Socrates is mortal, then either Socrates
is mortal or Socrates is fat. Compare the claim that Socrates is
mortal. While we believe the latter claim to be true, reason alone
does not justify this belief. Instead, we rely on experience—empirical
investigation. So, while it is a priori that if Socrates is mortal,
then either Socrates is mortal or Socrates is fat, it is a posteriori
that Socrates is mortal. We may also speak of truths that are a priori
deducible from other truths. For example, although "Socrates is
mortal" is a posteriori, that same truth is a priori deducible from
two other truths: "All men are mortal" and "Socrates is a man." In
other words, the latter two truths, taken together, a priori entail
that Socrates is mortal.
Second, there is the notion of metaphysically necessary truths. A
necessary truth is a truth that could not have failed to be the case.
Logical truths again provide clear examples: "Either Socrates is
mortal or it is not the case that Socrates is moral" is usually
regarded as necessary. Contrast that truth with "Socrates is mortal."
The latter is not necessary. Truths that are not necessary are also
known as contingent. Philosophers often distinguish between different
strengths or kinds of necessity. For example, there is arguably a
sense in which it is a necessary truth that pigs cannot fly like
birds. But if the laws of nature were different, then perhaps pigs
would be able to fly like birds. So, perhaps it is not metaphysically
impossible that pigs should be able to fly like birds. A
metaphysically necessary truth is a truth that is necessary in the
strictest possible sense: a truth that holds not just because of
contingent laws of nature. Saul Kripke (1972) famously argues that
there are metaphysically necessary truths that are not truths of pure
logic. Indeed, he argues that there are metaphysically necessary
truths that are not a priori. For example, on his view, that water is
H2O is metaphysically necessary but a posteriori. He recognizes that
there could have been substances that resemble water—substances that
share water's superficial qualities, such as its taste and visual
appearance—but with a different molecular structure. But, he argues,
these substances would not be water.
Third, let us introduce some abbreviations. On Jackson's version of
the knowledge argument, the assumption that Mary knows the complete
physical truth about the world does not guarantee that she will be
able to figure out the complete truth about human color vision. His
reasoning involves the idea of the complete physical truth. Call the
complete physical truth P. P can be seen as a long conjunction of all
the particular physical truths, which, according to Jackson, Mary
learns from watching science lectures. What about the truths that,
according to Jackson, Mary does not learn until she leaves the room?
Those would be included in the psychological truths about the world.
Call the complete psychological truth Q. Finally, consider what
Stoljar and Nagasawa call "the psychophysical conditional": if P then
Q, where P is the complete physical truth and Q is the complete
psychological truth. As we will see, part of Jackson's reasoning can
be understood in terms of his view about the psychophysical
conditional.
We are now in a position to state the second of Jackson's distinctive
contributions to the discussion of the knowledge argument. This
contribution concerns his inference from the knowledge intuition to
physicalism's falsity. His inference assumes that if physicalism is
true then the complete truth about human color vision is a priori
deducible from the complete physical truth. But here a problem arises:
why accept this assumption? Consider the psychophysical conditional,
if P then Q (again, P is the complete physical truth and Q is the
complete psychological truth). As Jackson conceives of physicalism,
physicalism entails that the psychophysical conditional is a priori.
If he is right, then all truths about color vision would be deducible
from P (the complete physical truth). But here physicalists have a
natural, obvious response: why not instead characterize physicalism as
a Kripkean a posteriori necessity, akin to water is H2O? On this
characterization, the psychophysical conditional is metaphysically
necessary but not a priori.
In later work, Jackson criticizes this response. His argument is
complex, but the basic idea is simple enough. In a 1995 "Postscript,"
he reasons as follows. Consider the argument:
H2O covers most of the planet.
Therefore, water covers most of the planet.
The premise necessitates, but does not a priori entail, the
conclusion. But, Jackson asks, why is there no a priori entailment? On
his view, there is no such entailment because the argument's premise
gives us only part of the physical story. It is also part of the
physical story that H2O does the other things that water does, that
is, that H2O plays the water role. Playing the water role includes
such things as being a substance that occupies oceans and lakes, looks
clear to us, has little or no taste, is referred to as "water", etc.
So, let us add the following premise to the argument displayed above:
H2O plays the water role.
Now, says Jackson, the premises do a priori entail the conclusion.
Moral: "a rich enough story about the H2O way things are does enable
the a priori deduction of the water way things are" (Jackson 1995, p.
413). Likewise, physicalism entails that "knowing a rich enough story
about the physical nature of our world is tantamount to knowing the
psychological story about our world" (Jackson 1995, p. 414). But if
physicalism is true, P should provide just that: a rich enough story.
Thus, Jackson concludes, physicalism entails the apriority of the
psychophysical conditional after all.
Jackson's argument is controversial. But in developing it, he fills an
important lacuna in the knowledge argument and thereby improves on
earlier versions. Others, too, have attempted to fill this lacuna.
Most notably, David Chalmers (1996, 2003, 2004, and 2006a) has given
sophisticated arguments to this end, which are partly inspired by
Jackson's argument.
3. Related Arguments
The knowledge argument is one of several ways to articulate the
suspicion that phenomenal consciousness is not physical. Another
common way of articulating the doubt is through the conceivability
argument. This argument descends from René Descartes' main argument
for mind-body substance dualism. He argued that, since he can clearly
and distinctly conceive of his mind without his body and his body
without his mind, they can exist without each other and are therefore
distinct substances.
Contemporary versions of the conceivability argument usually rely on
thought experiments concerning qualia. One such thought experiment
involves inverted qualia. It seems conceivable that there be an
individual exactly like me, except he and I are red/green inverted. We
are physically and functionally identical, but the color experiences
he has when viewing a ripe tomato (in normal light, without special
contact lenses, and so forth) resemble the color experiences I have
when viewing a ripe zucchini, and vice versa. Such a person would be
my inverted twin. Likewise, it seems conceivable that there be a world
exactly like ours in all physical and functional respects but without
phenomenal consciousness. Creatures that lack consciousness but are
physically and functionally identical to ordinary human beings are
called zombies. If it is conceivable that there be creatures such as
my inverted twin or my zombie twin, then, the conceivability argument
runs, this supports the metaphysically possibility of such creatures.
And most agree that if such creatures are metaphysically possible,
then phenomenal consciousness is neither physical nor functional:
physicalism is false.
Yet another related argument is the explanatory argument. This
argument begins with the premise that physicalist accounts explain
only structure (such as spatiotemporal structure) and function (such
as causal role). Then it is argued that explaining structure and
function does not suffice to explain consciousness, and so physicalist
accounts are explanatorily inadequate.
As Chalmers (2003) notes, the knowledge argument, the conceivability
argument, and the explanatory argument can be seen as instances of a
general, three-step argument. The first step is to establish an
epistemic gap between the physical and phenomenal domains. In the case
of the knowledge argument, the gap is often put in terms of a priori
deducibility: there are phenomenal truths that cannot be a priori
deduced from physical truths. In the case of the conceivability
argument, the gap is put in terms of conceivability: it is conceivable
that there be inverted qualia or zombies. And in the case of the
explanatory argument, the point is put in terms of an explanatory gap.
After establishing an epistemic gap, these arguments take a second
step and infer a corresponding metaphysical gap: a gap in the world,
not just in our epistemic relation to it. The knowledge argument
infers a difference in type of fact. The conceivability argument
infers the metaphysical possibility of inverted qualia or zombies. And
the explanatory argument infers that there are phenomena that cannot
be physically explained. As a third step, all three results appear to
conflict with physicalism. There are important differences among the
arguments, and it is not obvious that they stand or fall together.
Nevertheless, it is worth noting that they follow a single abstract
pattern.
4. More Physicalist Responses
Most physicalist responses to the knowledge argument fall into three
categories: those that reject the inference to physicalism's falsity
and thus deny the metaphysical gap; those that reject the knowledge
intuition and thus deny the epistemic gap; and those that derive an
absurdity from Jackson's reasoning.
We have already noted one way of rejecting the inference from the
knowledge intuition to physicalism's falsity: one could defend a
version of physicalism on which the psychophysical conditional is
necessary but not a priori. There are other ways of rejecting the
inference. One is to reject the assumption that phenomenal knowledge
is propositional knowledge—knowledge of truths or information. That
is, one could argue that the type of knowledge Mary gains when she
leaves the room is non propositional. The most popular version of this
view is based on the ability hypothesis, the claim that to know what
it's like is to possess certain abilities, such as the ability to
imagine, recognize, and remember experiences. On this view, Mary's
learning consists in her acquiring abilities rather than learning
truths. As the view is sometimes put, she gains know-how, not
knowledge-that. There are other versions, including the view that upon
leaving the room Mary acquires only non propositional acquaintance
knowledge (Conee 1994, Bigelow and Pargetter 1990). On this version,
her learning consists, not in acquiring information or abilities, but
in becoming directly acquainted with the phenomenal character of color
experiences, in the way that one can become acquainted with a city by
visiting it.
These views allow the physicalist to accept the knowledge intuition
without facing objections that Jackson, Chalmers, and others bring
against a posteriori physicalism. But other problems arise. Regarding
the ability hypothesis, some doubt that Mary's learning could consist
only in acquiring abilities. Her new knowledge appears to have
characteristic marks of propositional knowledge because its content
can be embedded in conditionals such as "if seeing red is like this,
then it is not like that" (Loar 1990/97). And some philosophers
question the significance of the distinction between know-how and
knowledge-that on which the strategy of the ability-hypothesis seems
to rely (Alter 2001, Stanley and Williamson 2001).
The idea that Mary acquires only acquaintance knowledge has similar
difficulties. It is not clear that all she acquires is acquaintance
knowledge or that the requisite distinction between acquaintance
knowledge and propositional knowledge is tenable. Also, there is a
danger of trading on an ambiguity: sometimes "acquaintance" refers to
knowledge, sometimes to experience. On the former, epistemic
interpretation, it is unclear that Mary's new "acquaintance knowledge"
includes no factual component. And on the latter, experiential
interpretation, the acquaintance hypothesis trivializes the learning
claim: no one denies that when Mary leaves the room she has new
experiences.
Another way to reject the inference to physicalism's falsity is to
argue that Mary's learning consists in acquiring new ways to represent
facts she knew before leaving the room (Loar 1990, 1997, Lycan 1996,
Horgan 1984, McMullen 1985, Pereboom 1994, Tye 2002). This view is
often combined with an appeal to a posteriori necessity (see section 2
above). But it need not be: one could argue that while the
psychophysical conditional is a priori knowable by those who possess
the relevant phenomenal concepts, Mary lacks those concepts before
leaving the room. The main challenge for this view concerns the status
of her new concepts. It is not enough to say that she gains some new
concept or other: her conceptual gain must explain her gain in
knowledge. The concern is that any concepts adequate to the task—such
as the concept having an experience with phenomenal feel f—might
incorporate a non physical component (Chalmers 2006b).
Philosophers have also devised ways to reject the knowledge intuition.
Some believe that intuitions based on hypothetical cases should be
given little or no weight. Also, specific strategies for rejecting the
knowledge intuition have been developed. One is to reject the learning
claim: to argue that on reflection Mary does not learn anything when
she leaves the room. Some defend this position by arguing that we
simply underestimate the power of complete physical knowledge. Suppose
we try to fool Mary by greeting her when she leaves the room with a
blue banana. Would she be fooled into thinking that seeing yellow is
what we would describe as seeing blue? Not necessarily. She could use
a brain scanner (perhaps a descendent of a PET device) to examine her
own brain processes. She would notice that her brain processes
correspond to people having blue experiences, and thereby evade our
trap. Maybe our intuition that she learns something fails to take this
sort of consideration into account (Dennett 1981, 2006). But other
philosophers doubt that the intuition derives from any such error.
Another way to reject the knowledge intuition is to challenge the
complete-knowledge claim: to argue that not all physical facts about
seeing colors can be learned by watching black-and-white lectures. On
this view, a fact might be physical but not discursively learnable.
How could this be?
Some (for example, Horgan, 1984) use "physical" broadly, so that that
the physical truths include high-level truths necessitated by the
microphysical truths. These physicalists argue that phenomenal truths
are themselves high-level physical truths, and that it is
question-begging to assume that Mary knows all the physical truths
simply because she watches lectures on chemistry, physics, etc.
Chalmers (2004, 2006a) suggests a natural response to this move: use
"physical" narrowly, so that the physical truths include only the
microphysical truths (or those plus the truths in chemistry or some
other specified domains). It is harder to deny that such truths would
be accessible to the pre-release Mary. Of course, this entails that
high-level biological truths, for example, will count as non physical,
and thus the existence of non physical truths will not itself defeat
physicalism. But if Jackson's reasoning is sound, then there are
phenomenal truths that are not metaphysically necessitated by the
narrowly physical truths—and that result would defeat physicalism.
On another version of the view that the complete-knowledge claim is
false, Mary's science lectures allow her to deduce the truths
involving structural-dynamical properties of physical phenomena, but
not their intrinsic properties. The knowledge argument does not appear
to refute this view. If this view can reasonably be called a
physicalist view, then there is at least one version of physicalism
that the knowledge argument appears to leave unchallenged. However, it
is unclear that this is a significant deficiency. Arguably, on the
view in question, consciousness (or protoconsciousness) is a
fundamental feature of the universe—or at least no less fundamental
than the properties describable in the language of physics, chemistry,
etc. That sounds like the sort of view the knowledge argument should
be used to establish, not refute. (It is a form of neutral monism; see
next section.)
5. Non Physicalist Responses
If we accept the knowledge argument, then how should we understand the
relationship between consciousness and the physical world? Jackson
(1982) defends epiphenomenalism, on which phenomenal properties or
qualia are caused by but do not cause physical phenomena. But
epiphenomenalism is only one non physicalist view that the knowledge
argument leaves open. Others include interactionism, parallelism, and
idealism. These views agree that consciousness is not reducible to the
physical, but disagree over how the two interact causally. On
interactionist dualism, consciousness affects the physical world and
vice versa. On parallelism, physical events and events of
consciousness run in parallel but do not affect each other. On
idealism, there are only conscious phenomena. The knowledge argument
also leaves open neutral monism, the view that phenomenal properties
(or protophenomenal properties) are the categorical, intrinsic bases
of physical properties, which are at bottom dispositional and
relational. This view might or might not be considered a version of
physicalism, depending on whether the intrinsic nature of physical
properties is considered physical.
All of these views have significant costs and benefits. For example,
interactionist dualism is commonsensical but hard to reconcile with
the popular view that the physical world is causally closed, that is,
the view that every physical event has a sufficient physical cause. To
take another example: epiphenomenalism preserves causal closure but
seems to conflict with the widespread naturalistic assumption that
consciousness is an integrated part of the natural world. Accepting
the knowledge argument forces philosophers to weigh such costs and
benefits and develop new, non physicalist accounts.
Historically, epiphenomenalism is associated with Huxley (1874),
interactionist dualism with Descartes (1641), parallelism with Leibniz
(1714), idealism with Berkeley (1713), and neutral monism with Russell
(1927). For more recent versions, see Jackson (1982) and Robinson
(1982b, 1988) for epiphenomenalism; see Popper and Eccles (1977), Hart
(1988), Foster (1991), and Hodgson (1991) for interactionist dualism,
see Rosenberg (2004) for neutral monism; and see Adams (forthcoming)
for idealism. There are no recent defenses of parallelism.
6. Other Responses
Some claim that Jackson's position is internally inconsistent (Watkins
1989, Campbell 2003). The argument runs roughly as follows. On the
knowledge argument, Mary acquires knowledge when she leaves the room
because she has states with new qualia. But this is impossible if, as
Jackson (1982) suggests, epiphenomenalism is true: on
epiphenomenalism, qualia are causally inefficacious; so, how can
qualia produce an increase in knowledge? So, Jackson cannot
consistently maintain both epiphenomenalism and the learning claim.
However, the sort of epiphenomenalism Jackson defends implies, not
that phenomenal features are inefficacious, but only that they have no
effects on physical phenomena. He might therefore reply that
phenomenal knowledge is not a physical phenomenon, and thus qualia may
indeed cause Mary to acquire it. Also, he can reasonably complain that
the objection assumes a causal theory of knowledge that is not
appropriate for phenomenal knowledge.
Despite the availability of these replies, there is a serious problem
in the vicinity of the inconsistency objection. We should expect
physical or functional explanations of our judgments about qualia. But
if the knowledge argument is sound, then qualia would seem to be
explanatorily irrelevant to these judgments—including the judgment
that qualia cannot be explained in physical or functional terms. This
is what David Chalmers calls "the paradox of phenomenal judgment"
(Chalmers 1996, chapter 5). It appears to be a real problem, which
arises for any non physicalist theory of consciousness.
Another important response to the knowledge argument should be noted.
The argument seems to assume that "physical" has a clear meaning. But
whether this notion can be adequately defined is not obvious. One
problem is "Hempel's dilemma" (Hempel 1980, Montero 1999). Arguably,
we should not define the physical in terms of current physics, because
current physics will be extended and presumably revised in substantial
ways. We could define it in terms of ideal physics. But who knows what
ideal physics will look like? Future physics may involve novel
concepts that we cannot begin to imagine. If "physical" is defined in
terms of such unknown concepts, then how can we judge whether Mary
could learn all the physical facts from black-and-white lectures? And
how else should we define the notion except by appeal to (current or
ideal) physics?
Some take such considerations to show that the debate over whether
consciousness is physical is misguided or meaningless (Chomsky 1980,
1988, Crane and Mellor 1990, Montero 1999). But the difficulty may be
surmountable. On one view, ideal physics will not be wholly
unrecognizable: like today's physics, it will be concerned entirely
with structure and dynamics. And one may be able to argue that any
structural/dynamical properties can in principle be imparted by
black-and-white lectures.
7. Jackson's Retraction
As we noted earlier, Jackson (1998, 2003, 2006) has come to embrace
physicalism and reject the knowledge argument. More specifically, he
rejects the claim that Mary learns new truths when she leaves the
room. He argues that this claim derives from a mistaken conception of
sensory experience—a conception that he thinks should be replaced with
representationalism, the view that phenomenal states are
representational states. Interestingly, he combines this view with the
ability hypothesis. He writes,
Those who resist accounts in terms of ability acquisition tend to
say things like "Mary acquires a new piece of propositional knowledge,
namely, that seeing red is like this", but for the representationalist
there is nothing suitable to be the referent of the demonstrative.
We have ended up agreeing with Laurence Nemirow and David Lewis
[the authors of the ability-hypothesis strategy] on what happens to
Mary on her release. But, for the life of me, I cannot see how we
could have known they were right without going via
representationalism. (Jackson 2003, p. 439)
It is unclear why Jackson's representationalism leads him to embrace
the ability hypothesis. Despite his commitments to physicalism and the
apriority of the psychophysical conditional, he has other options. For
example, instead of explaining Mary's epistemic progress in terms of
newly acquired abilities, he might argue that her "progress" is an
illusion; in other words, he might reject the learning claim.
Moreover, it may be possible to formulate a representationalist
version of the knowledge argument that inherits the force of the
original (Alter, 2006).
8. Summary of Assumptions and Criticisms
As we have seen, the knowledge argument depends on several
controversial assumptions. It will be useful to summarize some of
these assumptions and some criticisms of them. I will also mention
some sources for relevant arguments.
Assumption 1: The coherence of the notion of the physical: physicalism
is a substantive doctrine with non trivial content.
Criticism 1: The notion of the physical is not well defined, and there
is no substantive issue of whether physicalism is true (Chomsky 1980,
1988, Crane and Mellor 1990, Montero 1999). For replies, see Chalmers
(1996, 2004) and Stoljar (2000).
Assumption 2: The complete-knowledge claim ("truths" version): before
leaving the room, Mary knows all physical truths.
Criticism 2a: Pre-release Mary does not know all the physical truths,
because high-level physical truths cannot in general be a priori
deduced from low-level physical truths (Horgan 1984, van Gulick 2004,
Block and Stalnaker 1999). For replies, see Chalmers (2004, 2006a) and
Chalmers and Jackson (2001).
Criticism 2b: Pre-release Mary does not know all the physical truths,
because truths about the intrinsic properties of physical phenomena
cannot be discursively learned (Alter 1998, Stoljar 2000). For
replies, see Chalmers (1996, 2003, 2004, 2006a)
Assumption 3: The learning claim: upon leaving the room, Mary learns something.
Criticism 3a: We think Mary learns something because we fail to
appreciate the implications of knowing all physical truths (Foss 1989,
Stemmer 1989, Dennett 1991, 2004, 2006a). For replies, see Chalmers
(1996), Alter (1998), Robinson (1993), and Jacquette (1995).
Criticism 3b: We think Mary learns something because we fail to
recognize that phenomenal properties are just representational
properties (Jackson 2003). For a reply, see Alter (2006); and for a
counter-reply, see Jackson (2006).
Criticism 3c: Mary gains only unjustified beliefs (Beisecker 2000).
Assumption 4: The non-deducibility claim: if Mary learns new
phenomenal truths when she leaves the room, then those truths cannot
be a priori deduced from the complete physical truth.
Criticism 4: Mary cannot deduce certain phenomenal truths from the
complete physical truth only because she lacks the relevant concepts,
such as the concept of phenomenal redness. Thus, even though Mary
cannot deduce Q from P, the psychophysical conditional is a priori for
those who have the relevant concepts (Tye 2000, Hellie 2004). For
replies, see Chalmers (2004, 2006a) and Stoljar (forthcoming).
Assumption 5: The propositional-knowledge claim: the kind of knowledge
Mary gains upon leaving the room is propositional or factual—knowledge
of information or truths.
Criticism 5a: Mary gains only abilities (Lewis 1983, 1988, Nemirow
1990, Mellor 1993, Meyer 2001). For replies, see Jackson (1986),
Bigelow and Pargetter (1990), Loar (1990/97), Conee (1994),
Nida-Rümelin (1995), Lycan (1996), Alter (1998, 2001), Gertler (1999),
Tye (2002, chapter 1), Raymont (1999), and Papineau (2002). For
counter-replies, see Tye (2002, chapter 1) and Nemirow (2006).
Criticism 5b: Mary gains only acquaintance knowledge (Conee 1994,
Bigelow and Pargetter 1990). For replies, see Alter (1998), Gertler
(1999), and Papineau (2002).
Criticism 5c: Mary gains non propositional knowledge that does not fit
easily into folk categories (Churchland 1985, 1989).
Assumption 6: The new-information claim: the information Mary gains
upon leaving the room is genuinely new to her.
Criticism 6: Mary merely comes to know truths she already knew under
new, phenomenal representations. This view is sometimes called the
old-fact/new-representation view. It comes in at least two versions.
On one, phenomenal knowledge is assimilated to indexical knowledge:
Mary's "learning" is comparable to the absent-minded U.S. historian's
learning that today is July 4th, America's Independence Day (McMullen
1985). For replies, see Chalmers (1996, 2004, 2006a). Another version
attaches the old-fact/new-representation view to a posteriori
physicalism. Advocates of this version include Loar (1990/97), Lycan
(1996), Horgan (1984), and Pereboom (1994). For replies, see Alter
(1995, 1998) Chalmers (1996, 2003, 2004, 2006a) and Stoljar (2000).
Assumption 7: The claim that the knowledge intuition entails non
necessitation: if there are phenomenal truths that cannot be a priori
deduced from the complete physical truth, then the complete physical
truth does not metaphysically necessitate those phenomenal truths.
Criticism 7: Physicalism is an a posteriori necessity and is therefore
compatible with the claim that the phenomenal truths are not deducible
from the complete physical truth. For references, see the second
version of criticism 6 above.
Assumption 8: The consistency claim: the knowledge argument and non
physicalism are consistent.
Criticism 8: The assumption that Mary gains knowledge is inconsistent
with epiphenomenalism (Watkins 1989, Campbell 2003). For replies, see
Nagasawa (n.d.).
The knowledge argument rests on other assumptions. One is that if Mary
gains new, non physical information, then there are non physical
properties. Another is that if there are truths that are not
metaphysically necessitated by the complete physical truth, then
physicalism is false. But doubts about these assumptions may be
terminological variants on doubts about assumptions 1-8.
Some critics combine elements of different criticisms. For example,
Michael Pelczar's (forthcoming) criticism appears to contain elements
of the acquaintance hypothesis and the old-fact/new-representation
view; Jackson both rejects the learning claim and endorses the ability
hypothesis (Jackson 2003); and Robert van Gulick (2004) argues that
the various physicalist criticisms of the knowledge argument can be
seen as parts of a single, coherent reply. Those who endorse the
knowledge argument (in addition to Jackson, before he changed his
mind) include Robinson (1982a), Nida-Rümelin (1995), Chalmers (1996,
2004, 2006a), and Gertler (1999).
William Lycan (2003) writes, "Someday there will be no more articles
written about the "Knowledge Argument"… That is beyond dispute. What
is less certain is, how much sooner that day will come than the heat
death of the universe" (Lycan 2003). At least for now, however, the
knowledge argument continues to inspire fruitful reflection on the
nature of consciousness and its relation to the natural world.
9. References and Further Reading
* Adams, Robert. 2006. "Idealism Vindicated." Forthcoming in D.
Zimmerman and P. van Inwagen (eds) Persons: Human and Divine. Oxford:
Oxford University Press.
* Alter, Torin. 1998. "A Limited Defense of the Knowledge
Argument", Philosophical Studies, 90, 35-56
* Alter, Torin. 2001. "Know-How, Ability, and the Ability
Hypothesis", Theoria, 67, 229-39.
* Alter, Torin. 2006. "Does Representationalism Undermine the
Knowledge Argument?" Forthcoming in T. Alter and S. Walter (Eds.)
Phenomenal Concepts and Phenomenal Knowledge: New Essays on
Consciousness and Physicalism. New York: Oxford University Press.
* Beisecker, David. 2000. "There's Something about Mary:
Phenomenal Consciousness and Its Attributions", Southwest Philosophy
Review, 16, 143-52.
* Berkeley, George. 1713. Three Dialogues between Hylas and Philonous.
* Block, N. & Stalnaker, R. 1999. Conceptual Analysis, Dualism,
and the Explanatory Gap. Philosophical Review 108: 1-46.
* Brainspotting. 1994. U.K. television series.
* Broad, C. D. 1925. The Mind and its Place in Nature, London:
Routledge and Kegan Paul.
* Bigelow, John, and Robert Pargetter. 1990. "Acquaintance with
Qualia", Theoria, 61, 129-47.
* Campbell, Neil 2003. "An Inconsistency in the Knowledge
Argument", Erkenntnis, 58, 261-66.
* Chalmers, David J. 1996. The Conscious Mind: In Search of a
Fundamental Theory, New York: Oxford University Press.
* Chalmers, David J. 2002. "Consciousness and it Place in Nature"
in S. Stich and T. Warfield (eds.), The Blackwell Guide to the
Philosophy of Mind, Oxford: Blackwell. Reprinted in D. Chalmers (ed.),
The Philosophy of Mind: Classical and Contemporary Readings, (2002):
247–272, New York: Oxford University Press.
* Chalmers, David J. 2004. "Phenomenal Concepts and the Knowledge
Argument." In Ludlow, et. al. (2004).
* Chalmers, David J. 2006a. "The Two-Dimensional Argument against
Materialism." Forthcoming in his The Character of Consciousness. New
York: Oxford University Press.
* Chalmers, David J. 2006b. "Phenomenal Concepts and the
Explanatory Gap". Forthcoming in T. Alter and S. Walter Phenomenal
Concepts and Phenomenal Knowledge: New Essays on Consciousness and
Physicalism. New York: Oxford University Press.
* Chalmers, D.J. and Jackson, F. (2001). Conceptual Analysis and
Reductive Explanation. Philosophical Review 110: 315-61.
* Chomsky, Noam. 1980. Rules and Representations, New York:
Columbia University Press.
* Chomsky, Noam. 1988. Language and Problems of Knowledge: The
Managua Lectures, Cambridge, MA: MIT Press.
* Churchland, Paul. 1985. "Reduction, Qualia, and the Direct
Introspection of Brain States", Journal of Philosophy, 82, 8-28.
* Churchland, Paul. 1989. "Knowing Qualia: A Reply to Jackson", in
A Neurocomputational Perspective, Cambridge: MIT Press, 67-76.
* Conee, Earl. 1994. "Phenomenal Knowledge", Australasian Journal
of Philosophy, 72, 136-50.
* Crane, Tim and Hugh Mellor 1990. "There is no question of
physicalism", Mind, 99, 185-206.
* Dennett, Daniel C. 1991. Consciousness Explained, Boston: Little
Brown and Company.
* Dennett Daniel C. 2005. Sweet Dreams: Philosophical Obstacles to
a Science of Consciousness. Cambridge, MA: MIT Press.
* Dennett, Daniel C. 2006. "What RoboMary Knows". Forthcoming in
T. Alter and S. Walter (Eds) Phenomenal Concepts and Phenomenal
Knowledge: New Essays on Consciousness and Physicalism. New York:
Oxford University Press.
* Descartes, René. Meditations on First Philosophy. 1641.
* Foster, J. 1991. The Immaterial Self: A Defense of the Cartesian
Dualist Conception of Mind. Routledge.
* Foss, Jeff. 1989. "On the Logic of What It Is Like to be a
Conscious Subject", Australasian Journal of Philosophy 67, pp. 305-20.
* Gertler, Brie 1999. "A Defense of the Knowledge Argument",
Philosophical Studies, 93, 317-36.
* Hart, W. D. 1988. Engines of the Soul. Cambridge: Cambridge
University Press.
* Hellie, Benj 2004. "Inexpressible Truths and the Allure of the
Knowledge Argument." In Ludlow, et. al. (2004), 333-64.
* Hempel, Carl. 1980. "Comments on Goodman's Ways of Worldmaking",
Synthese 45:193-9.
* Hodgson, D. 1991. The Mind Matters: Consciousness and Choice in
a Quantum World. New York: Oxford University Press.
* Horgan, Terence 1984. "Jackson on Physical Information and
Qualia", Philosophical Quarterly, 34, 147-52.
* Huxley, Thomas H. 1874. "On the Hypothesis that Animals are
Automata, and its History". In D. Chalmers (ed.) The Philosophy of
Mind. New York: Oxford University Press, 2002, 24-30.
* Jackson, Frank. 1982. "Epiphenomenal Qualia", Philosophical
Quarterly, 32, 127-36.
* Jackson, Frank. 1986. "What Mary Didn't Know", Journal of
Philosophy, 83, 291-5.
* Jackson, Frank. 1995. "Postscript", in Contemporary Materialism,
ed. by Paul K. Moser and J. D. Trout, New York: Routledge, 184-9.
* Jackson, Frank. 1998. "Postscript on Qualia." In his Mind,
Method, and Conditionals: Selected Essays: 76-79. London: Routledge.
* Jackson, Frank. 2003. "Mind and Illusion", in Minds and Persons:
Royal Institute of Philosophy Supplement 53, ed. by Anthony O'Hear,
Cambridge: Cambridge University Press, 251-271.
* Jacquette, Dale. 1995. "The Blue Banana Trick: Dennett on
Jackson's Color Scientist," Theoria 61, pp. 217-30.
* Kripke, Saul. 1972. "Naming and Necessity". In The Semantics of
Natural Language. Ed. G. Harman and D. Davidson. Dordrecht: Reidel.
Reprinted as Naming and Necessity. Cambridge, MA: Harvard University
Press, 1980.
* Leibniz, G. 1714. The Monadology.
* Lewis, David. 1983. "Postscript to 'Mad Pain and Martian Pain.'"
In his Philosophical Papers, vol. 1. New York: Oxford University
Press, pp. 130-32.
* Lewis, David. 1988. "What Experience Teaches", Proceedings of
Russellian Society (University of Sydney), Reprinted in Lycan (1999);
Block, Flanagan and Güzeldere (1997)
* Loar, Brian. 1990. "Phenomenal States", in Philosophical
Perspectives IV: Action Theory and the Philosophy of Mind, ed. by
James Tomberlin, Atascadero: Ridgeview Publishing, 81-108.
* Loar, Brian. 1997. "Phenomenal States (Revised Version)", in The
Nature of Consciousness, ed. by Ned Block, Flanagan Owen and Güzeldere
Güven, Cambridge, MA: MIT Press, 597-616.
* Locke, John. 1690. An Essay Concerning Human Understanding.
* Lodge, David. 2001. Thinks… London: Secker and Warburg Random House.
* Ludlow, P., Y. Stoljar, and D. Nagasawa, eds. (2004) There's
Something about Mary: Essays on Phenomenal Consciousness and Frank
Jackson's Knowledge Argument. Cambridge: MIT Press.
* Lycan, William G. 1996. Consciousness and Experiences,
Cambridge, MA: MIT Press.
* Lycan, William G. "Perspectival Representation and the Knowledge
Argument," in Q. Smith and A. Jokic (eds.), Consciousness: New
Philosophical Essays (Oxford: Oxford University Press, 2003).
* McMullen, C. (1985), "'Knowing What It's Like' and the Essential
Indexical", Philosophical Studies 48, pp. 211-33.
* Mellor, D. H. 1993. "Nothing Like Experience." Proceedings of
the Aristotelian Society 93, pp. 1-16.
* Meyer, Uwe. 2001. "The Knowledge Argument, Abilities, and
Metalinguistic Beliefs", Erkenntnis, 55, 325-47.
* Montero, Barbara. 1999. "The Body Problem," Noûs, Vol. 33, No. 3
(1999) p. 183-20.
* Nagasawa, Yujin, n.d. The "Most Powerful Reply" to the Knowledge
Argument. ANU manuscript.
* Nagel, Thomas. 1974. "What Is it Like to Be a Bat?",
Philosophical Review, 83, 435-50.
* Nemirow, Lawrence. 1990. "Physicalism and the Cognitive Role of
Acquaintance", in Mind and Cognition: A Reader, ed. by William G.
Lycan, Oxford: Blackwell, 490-9.
* Nemirow, Lawrence. 2006. "So This is What it's Like: a Defense
of the Ability Hypothesis." Forthcoming in T. Alter and S. Walter
(eds) Phenomenal Concepts and Phenomenal Knowledge: New Essays on
Consciousness and Physicalism. New York: Oxford University Press.
* Nida-Rümelin, Martine 1995. "What Mary Couldn't Know: Belief
About Phenomenal States", in Conscious Experience, ed. by Thomas
Metzinger, Exeter: Imprint Academic, 219-41.
* Papineau, David. 2002. Thinking about Consciousness. New York:
Oxford University Press, 2002.
* Pelczar, Michael. "Enlightening the Fully Informed." Forthcoming
in Philosophical Studies.
* Pereboom, Derk 1994. "Bats, Brain Scientists, and the
Limitations of Introspection", Philosophy and Phenomenological
Research, 54, 315-29.
* Popper, K. and Eccles, J. 1977. The Self and its Brain: An
Argument for Interactionism. Springer.
* Raymont, Paul. 1999. "The Know-How response to Jackson's
Knowledge Argument", Journal of Philosophical Research, 24, 113-26.
* Robinson, Howard. 1982a. Matter and Sense. Cambridge: Cambridge
University Press.
* Robinson, Howard. 1993. "Dennett on the Knowledge Argument",
Analysis, 53, 174-7.
* Robinson, W. S. (1982b) "Causation, Sensations and Knowledge",
Mind 91, 524-40.
* Rosenberg, Gregg. 2004. A Place for Consciousness: Probing the
Deep Structure of the Natural World. New York: Oxford University
Press.
* Russell, Bertrand. 1927. The Analysis of Matter. London: Kegan Paul.
* Stemmer, Nathan (1989), "Physicalism and the Argument from
Knowledge" Australasian Journal of Philosophy 67, pp. 84-91.
* Stoljar, Daniel 2000. "Physicalism and the Necessary A
Posteriori," Journal of Philosophy, 97, 33-54.
* Stoljar, Daniel 2000. forthcoming. "Physicalism and Phenomenal
Concepts", forthcoming in Mind and Language.
* Stoljar, Daniel and Yujin Nagasawa. 2004. Introduction to
Ludlow, et al. (2004).
* Tye, Michael. 2000. Consciousness, Color, and Content,
Cambridge, MA: MIT Press.
* Van Gulick, Robert. 2004. "So Many Ways of Saying No to Mary".
In Ludlow, et. al. (2004).
* Watkins, Michael 1989. "The Knowledge Argument against the
Knowledge Argument," Analysis, 49, 158-60.
* Wilson, Edward O. Consilience: the Unity of Knowledge. New York:
Alfred A. Knopf.
No comments:
Post a Comment