Are Absent Qualia Impossible? Ned Block The Philosophical Review

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AreAbsentQualiaImpossible?
NedBlock
ThePhilosophicalReview,Vol.89,No.2.(Apr.,1980),pp.257-274.
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The Phi/osophi~aR/ eview, LXXXIX, No. 2 (April 1980)
DISCUSSION
ARE ABSENT QUALIA IMPOSSIBLE?
Ned Block
F
unctionalism is the doctrine that pain (for example) is identical
to a certain functional state, a state definable in terms of its causal
relations to inputs, outputs, and other mental states. The functional
state with which pain would be identified might be partially character-
ized in terms of its tendency to be caused by tissue damage, by its
tendency to cause the desire to be rid of it, and by its tendency to pro-
duce action designed to shield the damaged part of the body from what
is taken to cause it.'
Functionalism has been plagued by two "qualia" centered objections:
the Inverted Qualia Objection and the Absent Qualia Objection. The
Inverted Qualia Objection can be introduced by attention to the
familiar inverted spectrum hypothesis, the hypothesis that though you
and I have exactly the same functional organization, the sensation that
you have when you look at red things is phenomenally the same as
the sensation that I have when I look at green things. If this hypothesis
is true, then there is a mental state of you that is functionally identi-
cal' to a mental state of me, even though the two states are qualitatively
' More oreciselv. functionalism could be characterized as follows:
,,
Let T be a psychological theory, all of whose mental state terms are pre-
dicates. The ~amseyse ntence of T can be written as
ZF, . . . F, T(Fl . . . F,).
If Fi is the variable that replaced "having pain," then
xis in pain o BF, . . . F,[T(F . . . F,) & x has F].
Functionalism would identify the property of having pain with the property
expressed by the predicate on the right hand side of the biconditional. The
property expressed by the predicate on the right hand side of the biconditional
is a functional property. This sort of formulation is due to David Lewis (though
Lewis's proposal differs markedly in details). A detailed exposition of function-
alism can be found in "What is Functionalism?" the introduction to the
functionalism section of my Readings in Philosophy ofPsycholog~v, ol. I, (Harvard
University Press: Cambridge), 1980.
A and B are functionally identical states iff they have the same causal
relations to inputs, outputs, and other mental states. As footnote 1 indicates,
the "mental" in the last sentence's characterization of functional identity
is eliminable via a formulation that specifies a certain set of states without
saying explicitly that they are mental states. So A and B would be said to
be functionallv identical iff thev have the sake causal relations to in~utso. ut-
L ,
puts, and other states that are themselves specified in terms of causal role.
As footnote 1 also indicates, functional characterizations are relative to
NED BLOCK

or phenomenally different. So the functional characterizations of
mental states fail to capture their "qualitative" aspect. To put the
difficulty more boldly, one could define a qualitative state Q as the
state someone has just in case he has a sensation with the same quali-
tative character as my current heada~heI.f ~in verted qualia are possible,
then mental state Q is not identical with any functional state, and if
functionalism claims that every mental state is a functional state,
functionalism is false.
The Absent Qualia Objection proceeds along similar lines, beginning
with an argument that it is possible that a mental state of a person x
be functionally identical to a state of y, even though X'S state has quali-
tative character while y's state lacks qualitative character altogether.
Sydney Shoemaker's "Functionalism and Qualia" is an ingenious
defense of the functionalist point of view from these qualia-centered
objections. Shoemaker argues that the functionalist can live with the
possibility of inverted qualia. Briefly, Shoemaker's proposal is that the
functionalist should concede that the mental state Q (defined above)
is not identical to any functional state. But he argues that this concession
does not prohibit the functionalist from giving functional characteriza-
tions of pain, being appeared to red, and other common mental states
that have qualitative character (without having qualitative identity
conditions in the manner of Q.
While Shoemaker allows the possibility of inverted qualia and elab-
orates functionalism so as to accomodate them, he is not so tolerant of
absent qualia. He argues that absent qualia are logically impossible,
--
psychological theory. So A and B might be functionally identical with respect
to one theory, but not with respect to another. The seriousness of this problem
may not be clear to those whose main contact with functionalism is via
Lewis's functional definitions. Lewis defines pain as the state with causal role
R. But pain can be the state with causal role R as well as the state with
causal role R', without contradiction, just as George Washington is both the
first president and the father of our country. However, the version of func-
tionalism with which I am concerned here-and one to which Lewis is also
committed-identifies pain, not with a functionally characterized state, (a
state picked out by its causal role) but with afunctional state (a state consti-
tuted by its causal role). One way of stating a genuine functional state (or
rather, functional property) identity thesis is that it identifies the property
of being a pain with the property of having causal role R. And being a pain
cannot be identical to both having causal role R and having causal role R',
just as no property can be identical to both the property of being the first
president, and being the father of our country.
See Sydney Shoemaker's "Functionalism and Qualia," Philosophical
Studies 27 (1975), p. 293. Reprinted in Readings in Philosophy of Psycholou, vol. I,
op. cit.
ARE ABSENT QUA LIA IMPOSSIBLE?

and hence that no version of the Absent Qualia Objection can go
through. My main purpose is to rebut Shoemaker's argument against
the possibility of absent qualia. At the end of the paper, I sketch Shoe-
maker:~s olution to the Inverted Qualia Objection, showing that it fails
if absent qualia are indeed possible.
Shoemaker's argument against the possibility of absent qualia is this:
if absent qualia are possible, then the presence or absence of the quali-
tative character of pain would make no difference to its causal
consequences; and so, according to a causal theory of knowledge, we
could have no knowledge of the qualitative character of pain; but
given that we do have knowledge of the qualitative character of
pain (in any sense of "qualitative character" of interest to a discussion
of absent or inverted qualia), absent qualia are not possible.
I have no quarrel with any reasonable version of a causal theory of
knowledge, nor do I wish to doubt Shoemaker's assumption that we
have knowledge of the qualitative character of our pain. The crux of my
disagreement with Shoemaker is in his first premise: that if absent
qualia are possible, then the presence or absence of the qualitative
character of pain would make no difference to its causal conse-
quences. If absent qualia are possible, there could be a state functionally
identical to pain that lacks qualitative character (call it "ersatz
pain").4 But ersatz pain could be possible even though the qualitative
character of genuine pain Is crucial to producing the consequences that
are produced in another way by ersatz pain. This is the point on which
Shoemaker's argument runs aground.
I shall make this point plausible by sketching an "odd realization"
of human functional organization whose pains are arguably ersatz.
Consider a very simple version of machine functionalism5 which
states that each mental system is described by at least one Turing
machine table of a certain sort, and that each mental state of the
system is identical to one of the machine table states. Consider, for
example, the Turing machine specified by the table printed be10w.~
(The table is equivalent to four conditionals: for example "If the
machine is in S, and receives a dime input, then it emits a coke and stays
in S,.")
I owe the phrase "ersatz pain" to an unpublished paper by Larry Davis.
' See N..Block and J. Fodor, "What Psythological States are Not," Philo-
sobhical Review, LXXXI (1972), pp. 159-181.
Cf. R. J. Nelson, "Behaviorism, Finite Automata, and Stimulus Response
he or^," in Theory and Decision 6 (1975), pp. 249-267.
NED BLOCK

nickel Emit no output Emit a Coke
input Go to S, Go to S,
+
dime Emit a Coke Emit a Coke
input Stay in S, a nickel
Go to S,
One can get a crude picture of the simple version of machine func-
tionalism that I am talking about by considering the claim that S,=
dime-desire and S, =nickel-desire. Of course, no functionalist should
claim that a Coke machine desires anything. Rather, the simple version
of machine functionalism that I am sketching makes an analogous
claim with respect to a much more complex machine table.
Now imagine a body externally like a human body, say yours, but
internally quite different. The neurons from sense organs are connected
to a bank of lights in a hollow cavity in the head. The motor output
neurons are activated by buttons on a console in another section of the
cavity. On one wall of the cavity is a very large machine table that
describes a person, say you, and in a corner of the cavity, there is a
blackboard. In the cavity resipes a little man. We tell the man to "start"
in a certain state, say S ,,,,,,which happens to be the state that you are
now in. The man's job is as follows. He writes "1,975" on the black-
board, and looks to the bank of input lights to see what inputs are
currently occurring. He sees a pattern of lights that he has been trained
,,,.
to identify as input I He looks on the great machine table on the wall
for the box at the intersection of row 342 and column 1,975. In the box
,,,,,,."
is written "Go to S,,,,,; emit output 0 The little man erases the
"1,975" from the blackboard and writes "7,651." Then he goes to the
output console and presses the pattern of buttons that he has been
,,,,,,.
taught will produce output 0 Then he looks to the input board
to see what the next input is, and so on. Through the efforts of this little
man, the artificial body in which he lives behaves just as you would,
given any possible sequence of inputs. Indeed, since the machine table
that the little man follows describes you, it is easy to see that the
homunculus-headed system is functionally the same as you.
But though the homunculus-headed system is now in the same
functional state that you are in, does it have the same mental states that
you have? Suppose that you and your homunculus-headed doppel-
ganger are in different rooms, both connected to a third room by a two-
way TV system. An interrogator in the third room addresses a remark
carried to you by your TV set and also to your homunculus-headed
doppelganger by his TV set. Since you and your doppelganger are
ARE ABSENT QUA LIA IMPOSSIBLE?

functionally alike, you emit exactly the same sounds and movements in
response. The interrogator replies, and you and your doppelganger
continue to respond in indistinguishable manners. Of course, you are
understanding the interrogator's English sentences and expressing your
thoughts in English. But is your doppelganger understanding the
interrogator's English sentences? Is it having the same thoughts that
you are having? The little man need not understand the interrogator's
remarks. He can push the buttons and read the patterns of lights with-
out having any idea that they have any relation to a conversation in
English. Indeed, he can do his job without knowing what sort of a
system he is controlling, and without being able to understand English
at all. More relevantly to our current discussion of qualia, suppose
you have a nasty headache and are calling for aspirin; the homunculus-
headed system, of course, is in the same functional state as you, and
is uttering similar sounds. However, the homunculus who is pushing the
buttons needn't have any pain. Why should we suppose that the system
of which he is a part has a pain?7
There are two claims that I want to emphasize that I am not making.
First I do not intend to use the example in any direct way to suggest
that functionalism has special difficulties with qualia. The homunculus-
headed system seems as lacking in thought as in qualia, and so any
argument against functionalism based on such an example could as
well be couched in terms of absent thoughts as absent qualia. I do place
special emphasis on the example's relevance to absent qualia because
I am discussing Shoemaker's claim that absent qualia are impossible.
Second, I do not intend that the example or what I shall say about it
here should convince anyone that absent qualia (or thoughts) are
possible. Intuitions about such matters are easy to manipulate, and even
if our intuitions in these cases were immutable, a critical examination
of the some of the intuitions would be required to ground any argument
for absent qualia.'
This example combines features of one discussed in my "Troubles with
Functionalism," in C. W. Savage (ed.), Perception and Cognition: Issues in the
Foundations of Psychology, Minnesota Studies in the Philosophy of Science, vol. IX.
(University of Minnesota Press: Minneapolis, 1978) (reprinted in Readings in
Philosophy ofpsychology, vol. I, op. cit.) and an example discussed in my "Psycho-
logism and Behaviorism," submitted for publication. John Searle makes use
of a similar example in an unpublished paper.
An attempt at such an argument is to be found in "Troubles with Function-
alism," op. cit. I do argue that there is one type of homunculus-head whose
quLlia are more in doubt than its thoughts, namely what I call a "Psychofunc-
tional" simulation of us. A Psychofunctional simulation is one for which the
theory T of footnote 1 is an empirical psychological theory (rather than a
NED BLOCK

Rather, my point is this. I want the reader to see why it is reasonable
for philosophers to allow that absent qualia are possible without commit-
ting themselves to Shoemaker's first premise. According to his first
premise, if the homunculus-head has absent qualia, we can conclude that
absent qualia are possible, and therefore that the presence or absence
of the qualitative character of pain would make no difference to its
causal consequences. But surely the possibility of a homunculus-head
with absent qualia does not entail-nor does it give us any reason to
believe-that the causal role of our genuine pain is independent of its
qualitative character. The causal role of genuine pain may be crucially
dependent on its qualitative character, even if the homunculus-head's pains
are ersatz.
Perhaps an analogy will make the point clearer. Consider a hydraulic
computer or other logic device. Now, for some such device, an "absent
fluid" hypothesis may be true: that is, there may be a functionally
identical device that lacks fluid, for example, because it works electric-
ally. (Recall that the absent qualia hypothesis says that for some
state that has qualitative character, there can be a functionally identical
state that lacks qualitative character.) But no one in his right mind
would argue that since the absent fluid hypothesis is true, the presence
or absence of fluid would make no difference to the operation of the
hydraulic device. The hydraulic device will presumably have states
whose causal consequences depend crucially on the properties of the
fluid, even though there could be functionally identical states that did
not depend on any properties of fluid (but on electrical properties
instead). Similarly, mousetraps with springs can be functionally identi-
cal to mousetraps without springs. (So an "absent spring" hypothesis
is true.) But it would be silly to conclude that the presence or absence
of springs make no differences to the causal consequences of the states
of those mousetraps that have springs.
Shoemaker goes wrong in his implicit picture of what the friend of
absent qualia must be committed to. The picture is that qualia are like
the colors of wires in a computer which cannot be opened. The wires are
(say) red, though since their color makes no difference to the working
common sense theory). I argue that the science relevant to qualia may be
physiology rather than psychology, and if so, we have a reason to suppose
that homunculus-infested Psychofunctional simulations have thoughts (viz.,
a psychological theory true of us is true of them) but no corresponding
reason to suppose the homunculus-infested Psychofunctional simulation has
qualia. This problem could be avoided by moving from Psychofunctionalism
to Physiofunctionalism (for which the theory T is a physiological theory),
but that would be to go far too deep into human chauvinism.
ARE ABSENT QUALIA IMPOSSIBLE?

of the computer, they could have been some other color without making
any functional difference. Since we cannot open the con~puterw, e will
never know whether the wires are red or green or even whether they
have any color at all. The color is "epiphenomenal," and so, according
to a causal theory of knowledge, we can have no knowledge of it. My
point is that a sensible friend of absent qualia need not be committed
to any such epiphenomenal picture of qualia. Instead, he can think
of qualia as like the fluid in the hydraulic computer mentioned above;
the fluid is crucial to the working of the device, even though there could
be a functionally identical device that lacks fluid.
The friend of absent qualia that Shoemaker attacks thinks that our
pain could lack qualitative character and still have the same causal
consequences. The friend of absent qualia that I defend makes a much
more modest claim, that there could be a being that has ersatz pain.
But although the friend of absent qualia that I defend is more modest
than the one Shoemaker attacks, I am not failing to meet Shoemaker's
challenge head-on. For the point of Shoemaker's attack on absent
qualia is to defend functionalism. And the version of the absent qualia
claim that I am suggesting, though deflationary, is strong enough to
defeat functionalism. For if it is true that the homunculus-head can
have the functional state putatively identical to pain (functional state
S, let us say) yet have no state with qualitative character, then we have a
case of S without pain. Therefore, pain # S, and hence functionalism
is false.
I have just sketched what is wrong with Shoemaker's argument on its
most natural interpretation. However, there are other ways of under-
standing the argument which I will proceed to discuss. The different
versions of the argument can be seen as stemming from a three-way
ambiguity in the notion of "epiphenomenal" (my word, not Shoe-
maker's) in terms of which the argument can be couched. The main
premises of the argument are the one that I have just been criticizing,
that if absent qualia are possible, qualitative character is epiphenom-
enal (call this the AQpremise), and a causal theory of knowledge (CTK)
premise to the effect that what is epiphenomenal is unknowable. (The
final premise is that qualitative character Is knowable, so (conclusion)
absent qualia are impossible.) On one way of reading "epiphenomenal,"
the AQpremise is subject to just the difficulty I have been pointing out.
On another way of reading "epiphenomenal," the AQpremise is subject
to another difficulty having to do with physical or physiological dif-
ferences between pains and ersatz pains. On still another way of reading
"epiphenomenal," the AQpremise becomes trivially true, but the CTK
premise then becomes entirely question-begging.
NED BLOCK
Let me state Shoemaker's argument in roughly the way he puts it:
1. AQ Premise If absent qualia are possible, then the qualitative
character of pain is entirely independent of its causal powers.
2. CTK Premise If F is a feature of a mental state S, and F is entirely
independent of the causal powers of S, then F is not knowable.
3. The qualitative character of pain is knowable.
4. Therefore, absent qualia are not possible.
As I said above, the problem in understanding the argument lies in an
ambiguity in the notion of "epiphenomenal" being used, that is, in
what Shoemaker means by "entirely independent of the causal powers
of." Shoemaker explicates this phrase in his statement of the CTK
premise:
[I]f there could be a feature of some mental state that was entirely independent
of the causal powers of the state (i.e., was such that its presence or absence
would make no difference to the state's tendencies to bring about other states,
and so forth), and so was irrelevent to its 'functional identity', then such a
feature would be totally unknowable (if you like, this assumes a causal theory of
knowledge).
lo
So "F is entirely independent of the causal powers of S" is to be read:
"The presence or absence of F would make no difference to S's tenden-
cies to bring about other states and so forth," or as I shall abbreviate it:
"The presence or absence of F would make no difference to S's causal
role." Now there is at least one serious ambiguity here:
Strong Reading: S could lack F, and S's lacking F would make no
difference to S's causal role.
Weak Reading: There could be a state S- which is functionally
identical to S, such that S- lacks F, but nonethe-
less has the same causal role as S.
The Strong Reading is stronger than the Weak Reading because in
a possible world in which S lacks F yet has the same causal role, S
retains the functional identity it has in the actual world (because it has
the same causal role), so S itself satisfies the conditions on S- specified by
the Weak Reading. So the Strong Reading entails the Weak Reading,
that is, if F is entirely independent of the causal powers of S on the
Strong Reading, then F is entirely independent of the causal powers of S
on the Weak Reading as well (though not vice versa).
Now it is easy to see how a functionalist might miss this distinction,
for if S is taken td be a functional state type, the distinction is a dis-
tinction without a difference. For if S is a functional state type, and
The argument appears mainly on pp. 295-298 (this and other page
references are to the version in Philosophical Studies).
O' Shoemaker, op. cit., p. 298.
ARE ABSENT QUALIA IMPOSSIBLE?
S- is functionally identical to S, then S just is S-. Functional identity
of functional state types" entails identity simpliciter. For functional
state types are defined by their causal relations to inputs, outputs,
and other states, and functional identity is just identity of these causal
relations. So, since S- lacks F, then S (being identical to S-) could
lack F. Hence the Weak Reading would entail the Strong Reading.
And since as I mentioned above, the Strong Reading entails the Weak
Reading (even if S is not taken to be a functional state) the two readings
would be logically equivalent.
Of course, what I have just said should not be taken to challenge
the distinction between the Strong Reading and the Weak Reading.
For to take S to be a functional state would be illicit in the context
of Shoemaker's argument. In the premises of Shoemaker's argument
that make use of locutions of the form of "F is entirely independent
of the causal powers of S," S is a mental state, and to take mental states
to be functional states would be to beg the question, since the truth
of functionalism is just what is at issue.
Let us begin our more detailed examination of Shoemaker's argument
by adopting the Strong Reading. On the Strong Reading, Shoe-
maker's CTK premise looks reasonable enough (anyway, I won't
object to it). It says:
CTK Premise: If F is a feature of a mental state S, and S's lacking
F would make no difference to S's causal role, then F is not know-
able.
Now let us look at the AQ premise. As originally stated, it said
that if absent qualia are possible, then the qualitative character of
pain is entirely independent of its causal powers. Substituting in
the Strong Reading of "entirely independent of the causal powers
of," we get
Absent Qwllia Premise, Strong Reading: If absent qualia are possible,
then pain could lack qualitative character, and its lacking qualita-
tive character would make no difference to its causal role.
Now on this Strong Reading of the AQ premise, it is clearly false for
reasons that I have already given. If absent qualia are possible, one
can conclude at most'' that ersatz pain is possible, but not that genuine
"
A token state or event is datable and nonrecurrent. E.g., the pain I am
having now can't recur (though I could have a similar one later). The type
pain, on the other hand, can recur, in that I can have pain and have it again
tomorrow. The type pain might be identifred with the property common
to all token pains in virtue of which they are pains.
l2 The locution "absent qualia are possible" is actually used by Shoemaker
to mean that for some state Q that has qualitative character, there could be a
functionally identical state Q-that lacks qualitative character. It is in this sense