front of you. There’s a difference between the two shades, but it’s barely
noticeable. (The technical term sometimes used by experts in psychophysics
is JND, or “just noticeable difference.” The JND is a statistical
distinction, not an exact quantity.) The two shades (I’ll call them Green
No. 24 and Green No. 25) are the nearest possible neighbors on the
color chart; there’s no shade of green between them that you could discriminate.
Now I put my hands behind my back, mix the swatches, and
hold one up. Is it Green No. 24 or Green No. 25? The interesting discovery
is that conscious perception alone does not enable you to tell the difference.
This means that understanding consciousness may also involve
understanding the subtle and the ultrafine, not just the whole.
We now must move from the global to the more subtle aspects of
consciousness. If it is really true that some aspects of the contents of consciousness are ineffable—and many philosophers, including me, believe
this to be the case—how are we going to do solid scientific research
on them? How can we reductively explain something we cannot even
talk about properly?
The contents of consciousness can be ineffable in many different
ways. You cannot explain to a blind man the redness of a rose. If the linguistic
community you live in does not have a concept for a particular
feeling, you may not be able to discover it in yourself or name it so as to
share it with others. A third type of ineffability is formed by all those
conscious states (“conscious” because they could in principle be attended
to) so fleeting you cannot form a memory trace of them: brief
flickers on the fringe of your subjective awareness—perhaps a hardly detectable
color change or a mild fluctuation in some emotion, or a barely
noticeable glimmer in the mélange of your bodily sensations. There
might even be longer episodes of conscious experience—during the
dream state, say, or under anesthesia—that are systematically unavailable
to memory systems in the brain and that no human being has ever
reported. Maybe this is also true of the very last moments before death.
Here, however, I’m offering a clearer and better defined example of ineffability
to illustrate the Ineffability Problem.
You can’t tell me if the green card I’m holding up is Green No. 24 or
Green No. 25. It is well known from perceptual psychology experiments
that our ability to discriminate sensory values such as hues greatly exceeds
our ability to form direct concepts of them. But in order to talk
about this specific shade of green, you need a concept. Using a vague category,
like “Some kind of light green,” is not enough, because you lose the
determinate value, the concrete qualitative suchness of the experience.
In between 430 and 650 nanometers, human beings can discriminate
more than 150 different wavelengths, or different subjective shades, of
color. But if asked to reidentify single colors with a high degree of accuracy,
they can do so for fewer than 15. The same is true for other sensory
experiences. Normal listeners can discriminate about 1,400 steps of pitch
difference across the audible frequency range, but they can recognize
these steps as examples of only about 80 different pitches. The University
of Toronto philosopher Diana Raffman has stated the point clearly:“We are much better at discriminating perceptual values (i.e. making
same/different judgments) than we are at identifying or recognizing
them.”Technically, this means we do not possess introspective identity criteria
for many of the simplest states of consciousness. Our perceptual
memory is extremely limited. You can see and experience the difference
between Green No. 24 and Green No. 25 if you see both at the same
time, but you are unable consciously to represent the sameness of Green
No. 25 over time. Of course, it may appear to you to be the same shade
of Green No. 25, but the subjective experience of certainty going along
with this introspective belief is itself appearance only, not knowledge.
Thus, in a simple, well-defined way, there is an element of ineffability in
sensory consciousness: You can experience a myriad of things in all their
glory and subtlety without having the means of reliably identifying
them. Without that, you cannot speak about them. Certain experts—
vintners, musicians, perfume designers—can train their senses to a
much finer degree of discrimination and develop special technical terms
to describe their introspective experience. For example, connoisseurs
may describe the taste of wine as “connected,” “herby,” “nutty,” or “foxy.”
Nonetheless, even experts of introspection will never be able to exhaust
the vast space of ineffable nuances. Nor can ordinary people identify a
match to that beautiful shade of green they saw yesterday. That individual
shade is not vague at all; it is what a scientist would call a maximally
determinate value, a concrete and absolutely unambiguous content of
consciousness.
As a philosopher, I like these kinds of findings, because they elegantly
demonstrate how subtle is the flow of conscious experience. They show
that there are innumerable things in life you can fathom only by experiencing
them, that there is a depth in pure perception that cannot be
grasped or invaded by thought or language. I also like the insight that
qualia, in the classic sense coined by Clarence Irving Lewis, never really
existed—a point also forcefully made by eminent philosopher of consciousness
Daniel C. Dennett. Qualia is a term philosophers use for
simple sensory experiences, such as the redness of red, the awfulness of
pain, the sweetness of peach pie. Typically, the idea was that qualia form recognizable inner essences, irreducible simple properties—the atoms
of experience. However, in a wonderful way, this story was too simple—
empirical consciousness research now shows us the fluidity of subjective
experience, its uniqueness, the irreplaceable nature of the single moment
of attention. There are no atoms, no nuggets of consciousness.
The Ineffability Problem is a serious challenge for a scientific theory
of consciousness—or at least for finding all its neural correlates. The
problem is simply put: To pinpoint the minimally sufficient neural correlate
of Green No. 24 in the brain, you must assume your subjects’ verbal
reports are reliable—that they can correctly identify the phenomenal
aspect of Green No. 24 over time, in repeated trials in a controlled experimental
setting. They must be able to recognize introspectively the
subjectively experienced “suchness” of this particular shade of green—
and this seems to be impossible.
The Ineffability Problem arises for the simplest forms of sensory
awareness, for the finest nuances of sight and touch, of smell and taste,
and for those aspects of conscious hearing that underlie the magic and
beauty of a musical experience. But it may also appear for empathy, for
emotional and intrinsically embodied forms of communication (see
chapter 6 and my conversation with Vittorio Gallese, page 174). Once
again, these empirical findings are philosophically relevant, because
they redirect our attention to something we’ve known all along: Many
things you can express by way of music (or other art forms, like dance)
are ineffable, because they can never become the content of a mental
concept or be put into words. On the other hand, if this is so, sharing the
ineffable aspects of our conscious lives becomes a dubious affair: We can
never be sure if our communication was successful; there is no certainty
about what actually it was we shared. Furthermore, the Ineffability Problem
threatens the comprehensiveness of a neuroscientific theory of consciousness.
If the primitives of sensory consciousness are evasive, in the
sense that even the experiencing subject possesses no internal criteria to
reidentify them by introspection, then we cannot match them with the
representational content of neural states—even in principle. Some internal
criteria exist, but they are crude: absolutes, such as “pure sweetness,”
“pure blue,” “pure red,” and so on. But matching Green No. 24 or Green No. 25 with their underlying physical substrates in a systematic manner
seems impossible, because these shades are just too subtle. If we cannot
do the mapping, we cannot do the reduction—that is, arrive at the claim
that your conscious experience of Green No. 24 is identical with a certain
brain state in your head.
Remember, reduction is a relationship not between the phenomena
themselves but between theories. T1 is reduced to T2. One theory—say,
about our subjective, conscious experience—is reduced to another—say,
about large-scale dynamics in the brain. Theories are built out of sentences
and concepts. But if there are no concepts for certain objects in
the domain of one theory, they cannot be mapped onto or reduced to
concepts in the other. This is why it may be impossible to do what most
hard scientists in consciousness research would like to do: show that
Green No. 24 is identical with a state in your head.
What to do? If identification is not possible, elimination seems to be
the only alternative. If the qualities of sensory consciousness cannot be
turned into what philosophers call proper theoretical entities because
we have no identity criteria for them, then the cleanest way of solving
the Ineffability Problem may be to follow the path that neurophilosopher
Paul Churchland and others suggested long ago—to deny the existence
of qualia in the first place. Would the best solution be simply to
say that by visually attending to this ineffable shade of Green No. 25 in
front of us, we are already directly in touch with a hardware property?
That is, what we experience is not some sort of phenomenal representational
content but neural dynamics itself? In this view, our experience of
Green No. 25 would not be a conscious experience at all but instead
something physical—a brain state. For centuries, when speaking about
“qualities” and color experiences, we were actually misdescribing states
of our own bodies, internal states we never recognized as such—the
walls of the Ego Tunnel.
We could then posit that if we lack the necessary first-person
knowledge, then we must define third-person criteria for these ineffable
states. If there are no adequate phenomenological concepts, let’s
form adequate neurobiological concepts instead. Certainly if we look
at the brain dynamics underlying what subjects later describe as their conscious experience of greenness, we will observe sameness across
time. In principle, we can find objective identity criteria, some mathematical
property, something that remains the same in our description
connecting the experience of green you had yesterday with the experience
you’re having right now. And then could we not communicate
our inner experiences in neurobiological terms, by saying something
like “Imagine the Cartesian product of the experiential green manifold
and the Möbius strip of calmness—that is, mildly K-314γ, but moving
to Q-512δ and also slightly resembling the 372.509-dimensional shape
of Irish moss in norm-space”?
I actually do like science fiction. This sci-fi scenario is conceivable, in
principle. But are we willing to give up our authority over our own inner
states—the authority allowing us to say that these two states must be the
same because they feel the same? Are we willing to hand this epistemological
authority over to the empirical sciences of the mind? This is the
core of the Ineffability Problem, and certainly many of us would not be
ready to take the jump into a new system of description. Because traditional
folk-psychology is not only a theory but also a practice, there may
be a number of deeper problems with Churchland’s strategy of what he
calls “eliminative materialism.” In his words, “Eliminative materialism is
the thesis that our commonsense conception of psychological phenomena
constitutes a radically false theory, a theory so fundamentally defective
that both the principles and the ontology of that theory will
eventually be displaced, rather than smoothly reduced, by completed
neuroscience.” Churchland has an original and refreshingly different
perspective: If we just gave up the idea that we ever had anything like
conscious minds in the first place and began to train our native mechanisms
of introspection with the help of the new and much more finegrained
conceptual distinctions offered by neuroscience, then we would
also discover much more, we would enrich our inner lives by becoming
materialists. “I suggest, then, that those of us who prize the flux and
content of our subjective phenomenological experience need not view
the advance of materialist neuroscience with fear and foreboding,” he
has noted. “Quite the contrary. The genuine arrival of a materialist kinematics
and dynamics for psychological states and cognitive processes will constitute not a gloom in which our inner life is suppressed or
eclipsed, but rather a dawning, in which its marvelous intricacies are finally
revealed—most notably, if we apply [it] ourselves, in direct selfconscious
introspection.”
Still, many people would be disinclined to turn something that was
previously ineffable into a public property about which they could communicate
using the vocabulary of neuroscience. They would feel that
this was not what they wanted to know at the outset. More important,
they might fear that in pursuit of solving the problem, we had lost something
deeper along the way. Theories of consciousness have cultural consequences. I will return to this issue.
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