The average human brain weighs in at something under three pounds and has a volume of 1,250 cubic centimeters (76 cubic inches). Despite the complexity of its architecture and the daunting interconnectedness of its 85 billion neurons, the goings-on in this small space have now been pretty well documented. We know what faculties are impaired when each part of the brain is injured, which neural activity, more or less, correlates with which behavior. Yet, as we discussed in our earlier dialogues, all these impressive results have not brought us any closer to accounting for consciousness or even establishing where exactly it “happens.”

How have scientists and philosophers dealt with this impasse? Some, like the philosopher Galen Strawson, have suggested that since it is self-evident that consciousness is real, and equally evident that neuroscience hasn’t accounted for it, there must be crucial things we don’t know about the physical world. Others, like the neuroscientist and psychiatrist Giulio Tononi, suppose consciousness must “emerge” from the highly integrated neural processes taking place in the brain, yet, as we noted in our last conversation, they don’t seem to have any conclusive empirical evidence. Others still, like the philosopher and cognitive scientist Daniel Dennett, deny that consciousness exists at all and insist that integrated selfhood is a delusion. While many of Dennett’s points make good sense, his claim that the issue of consciousness is mostly a matter of conceptual confusion has not brought us any closer to understanding the nature of conscious experience.

There are, however, a number of scientists and thinkers who’ve taken a different line. Not convinced that the consciousness problem will be solved by studying the brain alone, they have begun to look outside the head.

—Tim Parks

This is the fourth in a series of conversations on consciousness between Riccardo Manzotti and Tim Parks.

Tim Parks: Riccardo, how can one conceive of consciousness if it is not a brain-generated representation of the world outside?

Riccardo Manzotti: Let me offer a premise. I believe we are up against two equally strong, equally commonsensical, but incompatible intuitions. We feel that we, our selves, are located where our bodies are, and very likely inside our bodies. On the other hand, we don’t feel we are made of the kind of stuff we see when we look inside a human body. Our conscious experience is of quite a different nature from these cells, membranes, muscles, fat, and bodily fluids.

Parks: Could that be why we’re so fascinated by movies, paintings, even anatomy drawings that show the body being cut up or taken apart?

Manzotti: I’ve often thought so, yes. The real horror is not what’s there, the gruesome mess, but what’s missing! Rummaging through the body’s innards, we don’t see anything that resembles a self.

Parks: Traditionally the way round this has been to suppose that the mind, or even soul, is indeed in there, but invisible, insubstantial—made of non-physical stuff. Surely modern science couldn’t be accused of taking this position.

Manzotti: You would think not, yet recent neuroscience is perilously close to it. Consciousness, the neuroscientists claim, is inside the brain but eludes our observation. They see neural activity that correlates with consciousness, but acknowledge that this is not consciousness itself and don’t even try literally to observe consciousness itself. Since everything that is physical is detectable, this is akin to claiming that consciousness is not physical. And so we go back to Descartes and to dualism.

Parks: Let’s move on, then, to the obvious alternative: that we’ve been looking in the wrong place. Is the idea that the brain might not be the seat of consciousness a new one?

Manzotti: Not at all. If you like you could go as far back as Aristotle, who claims that the soul is, if only briefly, identical with the objects of our experience; the soul is “in a way all existing things; and knowledge is in a way what is knowable, and sensation is in a way what is sensible.” It’s worth remembering that for Aristotle the soul is material rather than spiritual, and thus akin to what we mean today by consciousness. So what he’s saying is that, at any given moment, our consciousness is identical with the form of what it is conscious of. When you see an apple, your consciousness and the apple are made of the same stuff, which he calls the form of the apple. If only, as he says, briefly.

Coming nearer to our own time, the behaviorists, B. F. Skinner in particular, argued against consciousness as something internal and against memories as things that are stored in the head. Like Dennett later, they played down the importance of phenomenological consciousness and concentrated on manifestations of selfhood in behavior. Essentially, they were reacting against notions such as “introspection,” “inner mental life,” and other remnants of German idealism, not to mention various unscientific forms of spiritualism. Yet by focusing exclusively on observable behavior, they threw the baby out with the bath water, ignoring consciousness altogether.

Parks: But where would consciousness be, exactly, if not in the head? What would constitute it?

Manzotti: In the second half of the twentieth century a number of thinkers, notably the psychologist James J. Gibson, began to focus on the interplay between body and environment. Rather than a representation of the world in the brain, a “movie in the head” as it were, perception was conceived as a skillful activity, or interaction with what is around us.

Parks: I do therefore I am!

Manzotti: Exactly. These thinkers are not denying or ignoring consciousness, as the behaviorists seem to be doing. Rather they talk a lot about our initial experience of the world, how as babies we discover our environment through touch and exploration, how all experience amounts to an engagement with what the world offers us.

Parks: Tell us who these people are. Talk us through it.

Manzotti: There are many versions of the same idea and plenty of fancy names: ecological perception, embodied cognition, externalism, enactivism, and the extended mind. Essentially, though, despite their many nuances, all of them are making the same claim: that what the body does constitutes, causes, or is the basis of the mind. Gibson, for example, worked with air force pilots and suggested that consciousness might be identical with the interplay between body and airplane or even with the interplay between plane and airstrip. Crucially, he introduced the notion of “affordance.” This is the idea that every external object offers or “affords” the body certain opportunities for active engagement. Crudely, you could think of how a pair of scissors offers itself to the thumb and fingers. Notice that this “affordance” depends on both body and object. For an animal that didn’t have the opponens pollicis—opposing thumb and fingers—the scissors would offer quite different possibilities and thus different affordances. Doorknobs, steps, bicycles, and keyboards all offer obvious cases of coupling between the body and external objects. Gibson’s point was that there was no need for these “affordances,” this matching of body and environment, to be represented in the brain, since they were already present externally in the meeting of body and object.

Parks: I’m sorry, but I can’t help noticing that all the examples you’ve given are man-made objects. Things made on purpose to fit our bodies.

Manzotti: I was trying to get the idea across as clearly as possible, but you’re right, there’s a problem here. Man-made objects are designed to have specific affordances that pull you toward them. In principle, you can see the affordances that, say, pebbles or bananas might offer a human being, or the ground beneath our feet for that matter. But such affordances are less clear in nature. Then of course there are many things—distant mountains, clouds in the sky—with which we have no interaction at all, yet we experience them just the same. Still, the biggest problem for Gibson’s approach is that the very idea of action is “mental.”

Parks: I don’t follow you.

Manzotti: Well, we can all see the persuasive power of the baby coming to consciousness through interaction with the external world. But we describe the child’s explorations as “actions” because we assume that he or she is a subject. What I mean is, the notion of action requires that first we have a subject, a conscious being. You wouldn’t say that a washing machine acts, but a person washing clothes does. A dog acts, or even a mouse, but not a glacier, or a wave moving across the sea.

Parks: So if the notion of action depends on consciousness, you can hardly use it to account for consciousness.

Manzotti: Right. However integrated we may be with our environment—and I believe we are—actions are not special things that can be used as building blocks to manufacture consciousness. They are events that happen because subjects do them to pursue their goals.

Parks: So this approach was short-lived?

Manzotti: The initial intuition that consciousness requires the external world we experience every day, that the mind isn’t simply locked in the skull as the internalists would have it, is a powerful and persuasive one; hence, after Gibson, there were lots of people eager to find ways round the problems this approach faced. In a seminal paper on behavioral and brain sciences published in 2001, J. Kevin O’Regan and Alva Noë offered a new version—they called it enactivism—that made a big impression on me at the time.

Parks: Why was that?

Manzotti: First they explicitly abandoned the idea that perception involves representations of the outside world created inside the brain by our neurons. That took courage. Instead, they proposed that seeing is a form of physical action. For example, they drew attention to the fact that our eyes are always in movement when we are looking, even though the object we are looking at appears to be still. I was impressed, in particular, by their claim that the skin is not some kind of magic threshold or insuperable barrier; on the contrary, there is a seamless, physical, causal continuity between what’s going on in the brain and what is happening in the world. When you see, photons bounce off the objects seen and pass through the air to meet the retina. When you hear, sound waves agitate the eardrum. And when you hold a tool in your hand, they pointed out, it actually becomes an extension of your experience. The Cartesian spell that kept subject and object apart, something the neuroscientists had reconstituted as the separation between brain and world, seemed on the point of dissolving.

Parks: It’s good to hear you enthusiastic for once. But I’m afraid I don’t get it. I can see that consciousness might be able to encompass certain prostheses. In the end even a pair of glasses becomes part of our system of perception; a pen or keyboard often seems an extension of oneself and I can imagine a seamless causal chain moving from my neurons to the pixels on my screen. I also take the point that our eyes are constantly mobile as they engage with the world. But I don’t see how that actually accounts for consciousness, for our experience of the world, or even of our bodies. I must say I’ve read Noë and really enjoyed his lively approach, but this was my problem throughout.

Manzotti: Well, you’re right to be skeptical. O’Regan and Noë ditched the term affordance, which carried a hint that the object was designed specifically to integrate with human action, and spoke instead of objects offering “sensory motor contingency.” But essentially it meant the same thing and didn’t solve the fundamental problem: if consciousness is constituted by actions, then for every experience there has to be a corresponding action. This sounds fine when we’re talking about things like surfing, skiing, carving the Sunday roast, or even kissing, but there are so many cases where it doesn’t work.

For example, I lick a strawberry ice cream and a chocolate ice cream. The action, licking, is the same, the sensory motor contingency, that is the affordance that the two ice creams present to the mouth, is the same, but the taste quite different. There simply isn’t a different action, a different engagement of the body with the environment, to match every different experience we have.

Parks: I presume we’re distinguishing, then, between the action of licking and the action, if you want to call it that, of the taste buds as they meet the different flavors?

Manzotti: From a mechanical perspective, different taste buds do not perform different actions. They are triggered by different molecules and are, of course, connected with different neural groups. But saying that a bitter taste is the outcome of bitter taste buds is tantamount to saying, as Johannes Peter Müller said in the nineteenth century, that the quality of our experience is provided by the peripheral nerves, an idea now entirely discredited, first and foremost by neuroscientists. The problem for the enactivist theory is that the tongue performs the same action no matter what ice cream is melting on it. And then that the properties of the experience—whether a chocolaty taste or a strawberry taste—are different from the properties of the physical action, licking.

Parks: All the same, action does shape and enrich our experience, doesn’t it? And we know that every action, every perception, subtly alters neural connections and pathways in our brain, such that we recognize at once when we have already done something before, touched a particular surface, tasted a particular ice cream.

Manzotti: Who could disagree? The problem is that what philosophers and scientists propose as the basis of consciousness—be it neurons or action—invariably turns out to be just one of many elements involved in delivering or tuning consciousness. Not the thing itself. Neurons obviously have a part; damage them and your consciousness will be changed. Actions have a part; as you say they shape and enrich consciousness. Culture and society also have a part; they mold and direct our consciousness. But none of these things is consciousness itself.

Parks: How did the enactivists handle dreams?

Manzotti: Well, here we have the obvious problem of experience without action. When we dream we are for the most part lying motionless. The eyes may be moving beneath the eyelids, but they are certainly not interacting with affordances in the immediate environment. In any event we now know that while most dreams take place during REM sleep, we can in fact dream in all phases of sleep. And of course dream experiences are hardly limited to the visual. In order to explain this special case then—experience without action—some enactivists have begun to distinguish between potential actions, or dispositions to act in response to the world’s affordances or sensory motor contingencies, and real actions or enacted actions.

Parks: So dreams become just one category of potential actions?

Manzotti: That’s it. When you are experiencing but not acting you are potentially acting. The problem is that in suggesting this solution they have created something separate from the physical world, a shadowy layer of possible, hypothetical actions waiting to be brought to life.

Parks: It sounds like we’re heading back to a separation between mental and physical, where the mental is everything we’re unable to account for.

Manzotti: To make matters worse, Noë speaks of our “possessing sensory-motor knowledge” rather than just interacting with the environment. This means that consciousness has now been relocated to a sort of abstract level—knowledge—which looks suspiciously like a mental repertoire of stored representations. It hardly matters whether these are representations of actions or sensory motor contingencies, rather than objects, they are still representations, namely something different from physical reality. This was precisely the kind of theory enactivism had set out to debunk.

Parks: It really does seem impossible to think about consciousness without falling back at some point into this Cartesian view, the real world out there and a representation of it in the head.

Manzotti: You can see why everyone is willing to give so much credit to the neuroscientists, or just scientists in general, hoping they will come up with something that will solve the dilemma, some as yet unknown aspect of the material world that will explain why consciousness is indeed in the head, but has nevertheless managed to remain invisible up to now.

Parks: I can see you don’t believe that’s going to happen. But at least it’s now clear that behind the problems encountered by all our thinkers, of whatever persuasion, is the vexed relationship between subject and object, the conundrum of how the world can be both out there and in our heads, apparently, at the same time. You feel that the enactivists’ decision to look for an answer outside the head was right, but that the focus on action was wrong. Let me propose then that in our next conversation we tackle that issue head-on: subject and object, inside and outside. Let’s consider every possible relation between the two. I also think, Riccardo, that it’s time you showed your hand and told us what you think. It is too easy breaking down other people’s ideas; you should give us something positive to chew over.

Manzotti: It will be a pleasure. But let me invoke Sherlock Holmes: “How often have I said to you that when you have eliminated the impossible, whatever remains, however improbable, must be the truth?”

Parks: Excellent. So in our next conversation we dispatch the last impossibilities and expect to be surprised.