The Ineffability problem: what we will never be able to talk about

Imagine I’m holding color swatches of two similar shades of green up in 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 15.¹³ 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.”¹⁴

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.¹⁵ 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.¹⁶ 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.”¹⁷ 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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