The Master and His Emissary: The Divided Brain and the Making of the Western World - Iain McGilchrist (2009)



LOOKING BACK OVER THE EVIDENCE I HAVE DISCUSSED IN THE PREVIOUS CHAPTER from philosophy, neurology and neuropsychology, it would appear that there is a good chance that the right hemisphere may be seeing more of the whole picture. Despite the left hemisphere's conviction of its own self-sufficiency, everything about the relationship of the hemispheres to one another and to reality suggests the primacy of the right hemisphere, both in grounding experience (at the bottom level) and in reconstituting left-hemisphere-processed experience once again as living (at the top level). We have also seen that many important aspects of experience, those that the right hemisphere is particularly well equipped to deal with – our passions, our sense of humour, all metaphoric and symbolic understanding (and with it the metaphoric and symbolic nature of art), all religious sense, all imaginative and intuitive processes – are denatured by becoming the object of focussed attention, which renders them explicit, therefore mechanical, lifeless. The value of the left hemisphere is precisely in making explicit, but this is a staging post, an intermediate level of the ‘processing’ of experience, never the starting point or end point, never the deepest, or the final, level. The relationship between the hemispheres is therefore highly significant for the type of world we find ourselves living in.

The left hemisphere is competitive, and its concern, its prime motivation, is power. If the working relationship were to become disturbed, so that the left hemisphere appeared to have primacy or became the end point or final staging post on the ‘processing’ of experience, the world would change into something quite different. And we can say fairly clearly what that would be like: it would be relatively mechanical, an assemblage of more or less disconnected ‘parts’; it would be relatively abstract and disembodied; relatively distanced from fellow-feeling; given to explicitness; utilitarian in ethic; over-confident of its own take on reality, and lacking insight into its problems – the neuropsychological evidence is that these are all aspects of the left hemisphere world as compared with the right.

What do we know of the relationship between the hemispheres in practice, and where could our knowledge, not of hemisphere differences, but of the working relationship of the hemispheres come from? There is limited mileage in looking at functional imaging, since its time frames are too large to detect most hemisphere interactions; and the EEG lacks specificity. There is a tendency simply to find, at any one moment in time, that areas in both hemispheres are involved (once again I would emphasise that everything human involves both hemispheres: we do virtually nothing with one hemisphere alone).

Just as what we know about the normal functioning of the brain comes from very particular accidents of nature, or from carefully contrived artificial experiments that highlight what otherwise goes unremarked, so what we know about relations between the hemispheres comes from careful observation of how they operate in highly specialised circumstances that allow their ‘working relationship’ to come under scrutiny. Some such evidence comes from carefully designed experiments on normal subjects in which the reactions of the hemispheres can be artificially separated and their interactions minutely observed. However, a particularly rich source has been split-brain patients.

My thesis is that the hemispheres have complementary but conflicting tasks to fulfil, and need to maintain a high degree of mutual ignorance. At the same time they need to co-operate. How is this achieved, and what is their working relationship like?

The corpus callosum, and the other subcortical structures, such as the cerebral commissures, which communicate between the hemispheres also have complementary but conflicting roles.1 They need to share information, but at the same time to keep the worlds where that information is handled separate. At the beginning of this book I referred to neurological evidence that the corpus callosum is largely inhibitory in function. That sounds competitive, but it might be co-operative, because co-operation requires difference, not more of the same. An action in one hemisphere is not usually best mirrored in the other: it is not co-operation for the surgeon and the assistant both to try to make the incision. In order to achieve many musical effects, whether between the singers in a choir, or the members of a string ensemble, or the two hands of a pianist, especially where there are fugal elements, discords, cross-rhythms and syncopations, it is equally vital for the performer to be sensitive to, and attentive to, one set of experiences, and simultaneously to be taken up in, and express, another, that may appear, at the local level, to be in conflict with it. We must inhibit one in order to inhabit the other. If one thinks of the relationship between the hemispheres as being like that between the two hands of the pianist (whose two hemispheres do indeed have to co-operate, but equally must remain independent), one can see that the task of the corpus callosum has to be as much to do with inhibition of process as it is with facilitation of information transfer, and co-operation requires the correct balance to be maintained.

We looked earlier at neurological evidence, but what of the phenomenological evidence – what actually happens in the world of the patient whose corpus callosum suddenly stops functioning? I mentioned that split-brain patients lead remarkably normal lives. If one met them, went out for a meal with them, or even went on holiday with them, one might never guess that there was anything unusual about them. Under certain laboratory conditions, in which the workings of the two hemispheres can be artificially isolated, we can learn about their independent function; but this apart, split-brain patients have not appeared particularly handicapped. Which invites the question, why ever not?

As far as sharing information goes, most experience of the external world is not confined to one hemisphere, and there is considerable redundancy in the system: ‘As we move around the world looking at objects, touching them, hearing sounds, and so forth, most of the information is taken in by both cerebral hemispheres. In addition, both hemispheres are usually able to generate some appropriate behavioural response.’2 We are not by any means completely reliant on callosal transmission. In fact, for this reason, experimental conditions for testing each hemisphere of a split-brain subject in isolation have to be carefully planned so that stimuli reach one hemisphere alone. And, as with all human beings, most of what each hemisphere knows, it knows in common with its counterpart. Both hemispheres, after all, have been through the same experiences, shared the same body, and indeed still are united in that body: everything below the corpus callosum – the diencephalon, the cerebellum, the brainstem, the spinal cord, and all the rest – and all that the body communicates to them second by second, they continue to share. Furthermore, as Sperry's colleague Joseph Bogen points out, even in normal subjects no connective pathways, even in the corpus callosum, function all the time; and lengthy neurotransmission times across the corpus callosum enforce a degree of interhemispheric independence.3

That is just as well because, as I have emphasised, there are good reasons why nature has conserved the great divide between the hemispheres. Each hemisphere has to remain independent, and inevitably remain to some extent ignorant, of what goes on in its counterpart. Inhibition is the other primary function, perhaps the principal function, of the corpus callosum.4 How does splitting it affect that?

In the long run, not as badly as one might think. By the time the brain is surgically divided, each hemisphere has had years of working with an intact corpus callosum during which to establish its own specialised modes of operation, laid down as memories in the patterns of neuronal connection within either hemisphere. So it is not the establishing, only the functional maintenance, of such specialisation that is impaired.

Nonetheless, in the first months following surgery, split-brain patients reported some rather disconcerting experiences. These took the form of an apparent conflict of will, displayed in so-called intermanual conflict. Such was the case of a man who found himself in the unfortunate position of going to embrace his wife with one arm and pushing her away with the other.5 Other patients with disruption of the corpus callosum have reported similar experiences, for example:

On several occasions while driving, the left hand reached up and grabbed the steering wheel from the right hand. The problem was persistent and severe enough that she had to give up driving. She reported instances in which the left hand closed doors the right hand had opened, unfolded sheets the right had folded, snatched money the right had offered to a store cashier, and disrupted her reading by turning pages and closing books.6

Or: ‘I open the closet door. I know what I want to wear. As I reach for something with my right hand, my left comes up and takes something different. I can't put it down if it's in my left hand. I have to call my daughter.’7 Notice that it is always the left hand that is ‘misbehaving’: I will return to that shortly.

These symptoms tended to settle with time. In fact split-brain patients manage surprisingly well, in that ‘despite having two independent and different cognitive processors, they behave as unified individuals and seldom display signs of hesitation, confusion or dissociation in their day-to-day activities’.8 This is because, although callosotomy severs the principal means of transfer of information between hemispheres, there are other subcortical tracts that connect them, sharing information and helping inhibit function, even if using some of these ‘detours’ takes some retraining of the brain.9

But the nature of the initial experience following operation bears further consideration, nonetheless. Such stories have been somewhat discounted, perhaps because of the tendency for commentators to rush into speculations about the divisibility of the self. However, Roger Sperry himself, who won a Nobel prize for his work on split brains, wrote, ‘both the left and right hemispheres may be conscious simultaneously in different, even in mutually conflicting, mental experiences that run along in parallel.’10 Such an idea clearly does raise questions about the self and personal identity, questions that have been much discussed, particularly by philosophers in the 1960s and 1970s when the research on split-brain subjects was getting to be known. But my purpose in referring to these experiences here is to suggest that the main evidence of disturbance following the operation was not, as might have been expected, things that no longer happened, but just the opposite – things that couldn't be prevented from happening, which, in other words, couldn't be inhibited. In this respect, split-brain subjects are like patients who have suffered a stroke or other neurological injury affecting the pathways through the corpus callosum: there is a problem of compromised interhemispheric inhibition.11 It is worse for those with callosal agenesis (a common condition, affecting up to 1 per cent of the population, in which the corpus callosum fails to develop),12 or those with congenital dysfunction of the corpus callosum: they have never had the advantage of living with a functional divide, and so cannot develop the usual interhemispheric inhibition in the first place.13

Incompetence of the corpus callosum has been implicated in the genesis of some psychiatric disorders, notably in the psychosis of schizophrenia; and this is in keeping with the fact that cases of psychosis have been found in association with complete and partial agenesis of the corpus callosum.14 If the main effect of an intact normal corpus callosum is inhibitory, its being compromised will have unpredictable results: either it will prove creatively fruitful, or it will simply be disruptive, by causing premature collapse into unity of elements or processes whose mutual independence needed to be maintained. Research in schizophrenia, using neuropsychological testing, as well as EEG and other measures, demonstrates precisely a failure of interhemispheric inhibition. In schizotypy, too, there is known to be intrusion of left-hemisphere modes into right-hemisphere functioning.15 Many of the phenomena of schizophrenia and of schizotypy – both the potentially creative (flying mathematicians) and the obviously disruptive effects (inhibited trapeze artists, see pp. 12–13) – could be explained by such intrusions, including intrusions of right-hemisphere modes into left-hemisphere functioning, as well as intrusion of left-hemisphere modes into right-hemisphere functioning.

In other words incompetence or agenesis of the corpus callosum leads to a picture of apparently increased interconnectivity of function.16 This apparently paradoxical finding makes sense if the main purpose of the corpus callosum is to maintain separation of the hemispheres.17

Independent functioning of the hemispheres is one of the achievements of maturity: children are, relatively speaking, split-brain subjects, with less interhemispheric independence.18 Babies and young children are less reliant on the corpus callosum: callosal myelination does not even begin until the end of the first year of life, and progresses only slowly thereafter.19 Pre-adolescent children find it relatively difficult to use their hemispheres separately, which is still further evidence of the inhibitory role played by the corpus callosum in adults.20 Interhemispheric connectivity grows during childhood and adolescence, with the result that the hemispheres become more independent.21 It may not be a coincidence that babies and young children are also more reliant on the right hemisphere, which matures earlier than the left, and it may be that it is the increasing importance of left-hemisphere function with age that necessitates the separation, in both hemispheres' interests, of their realms of activity. The Berlin Wall that meets this need would be the increasingly efficient corpus callosum.

All in all, my view is that the corpus callosum does act principally as the agent of hemisphere differentiation rather than integration, though ultimately differentiation may be in the service of integration. This complex, almost paradoxical, function at the very core of the brain, forming a bridge that nonetheless separates the worlds of the hemispheres, is captured with extraordinary prescience in one of the verses of the Hindu spiritual treatise The Upanishads: ‘In the space within the heart lies the controller of all …He is the bridge that serves as the boundary to keep the different worlds apart.’22


What do we know of the normal working relationship of the hemispheres, in those whose brains have not been artificially split? Is it one of harmony or discord? The question is not simple. Just as inhibition may be maintained in the interests of co-operation, co-operation may be maintained in the interests of competition: where two co-operate, the first may do so in a reciprocal spirit, while the second does so out of self-interest, that self-interest benefitting from the generosity of spirit of the first.

Moreover we have to distinguish between different levels of a relationship. Think of the relationship between two colleagues, who together run a small business. Which relationship are we talking about? At the simplest level one could describe the business partners' day-to-day mode of working together. So, for example, one could say that they share an office, and, what's more, share a breadth of training and experience in the work that they do, so that both can field enquiries. Each is acknowledged, nonetheless, to have special interests and expertise, and accordingly, where practicable, they split the work along agreed lines, especially where the work is complex; but where it would be quicker or more expedient, because, say, one of them is out of the office and an immediate response is needed, the other will step in and do whatever is required. At this level, and in this sense, the relationship appears pretty balanced and unproblematic.

But that might not be the relationship I'm thinking of. I mean, how do their roles interact, and how does each contribute to the work of the company as a whole? This is a rather different question, and takes us beyond the day-to-day, to something more like ‘month-to-month’ mode, a middle level.

Here, say, it might turn out that Franny is particularly interested in, and gifted at, bringing in new business; Fred, being a bit more of a backroom type, is better at doing the accounting and IT work. Without new business coming in, the outfit will fold; equally they will hardly survive without proper accountancy and IT support. So each needs the other. However, let's say that Fred has decided that the future lies in developing new and better accounting software systems, that that's what really matters. Anyone, he says to himself, can find the business; it takes someone special to keep the figures balanced, the systems running and ticking over. As a result Fred spends much of his time using the business data to help him develop more sophisticated software, and doesn't prioritise getting the figures ready for Franny's meetings with clients. He is given to feeling superior to Franny, telling himself there's nothing much she does that anyone couldn't do. At the same time Franny resents Fred spending so much of his time on what appear to be technicalities, freeloading on her ability to forge connections and make deals, and then letting her down at the last minute. There is an atmosphere in the office: bad-tempered exchanges, cool silences. And that represents another aspect of their relationship.

But there is a third level to this relationship; not the day-to-day, not even the month-to-month, but the long-term plan, which I just happen to have heard about. Unknown to Franny, Fred has decided he is going to take the company's data, ditch Franny, do a moonlight flit and start up an IT business all of his own.

I'm well aware that hemispheres are not people. Nor is this vignette supposed to sum up the relationship between the cerebral hemispheres. It is designed to do one thing only: to suggest that there would be different answers to the question how the hemispheres relate depending on the level at which we are looking. We need to look at the lowest level, the ‘day-to-day’ nitty-gritty of how they get through the work together – who answers the telephone. We need also to step back a bit, to the middle level, and look at how their roles complement one another in constructing our world – in theory, and, which may not be the same thing, in practice. And we should not forget to look at the long-term strategy, something that an outsider might know about before one of the partners.


If we start with level one, the ‘day-to-day’ – or in the case of the hemispheres, millisecond-to-millisecond – relationship, certainly their ‘takes’ on the world are both necessary to us from moment to moment as living human beings. It is not just that the three-dimensional space in which we move, as beings with bodies, requires bilateral engagement with the environment, and therefore bilateral engagement of the brain; our thinking processes, which define us as humans, involve the need for intuition and conceptualisation together. To the extent that the left hemisphere is the locus of conceptualised knowledge, and to the extent that the right hemisphere embodies intuitive perception, it is clear that both are necessary, and that a balance needs to be kept. Kant's famous formula, Begriffe ohne Anschauungen sind leer, Anschauungen ohne Begriffe sind blind (‘concepts without intuitions are empty; intuitions without concepts are blind’), applies here.23 Viewed from the standpoint of utility and task achievement, most ordinary tasks of daily life require ‘input’ from both spheres; and from the natural standpoint of everyday living, the world that we experience in the ordinary way is a fusion of what each hemisphere delivers. So it's clearly going to be in our best interests for the hemispheres to co-operate.24

I mentioned earlier, however, the nonchalance with which the left hemisphere makes up what is going on in the right hemisphere when in reality it has no idea. There is something intriguing about its reluctance to admit ignorance. Some subtle experiments looking at sequences of tasks that would normally call into action the two hemispheres differentially suggest that their mode of interaction is not one in which they co-operate over what each does best, like some parody of an ideal bureaucratic government, but instead is more like the real thing, one of rivalry between departments.25 The competition between the hemispheres can actually impair performance (which is no doubt why they are able mutually to inhibit one another).

I think it would be a mistake to attribute will to these millisecond-by-millisecond decisions. I do think a hemisphere can have a will, but it needs time to exert it. It is striking, on the one hand, that

a hemisphere assumes control of processing as a result of set or expectation as to the nature of the processing requirements prior to actual information processing, and …it remains in control even if its performance, for whatever reasons, is considerably worse than that which could have been produced by the opposite side of the brain.26

It's as if each hemisphere took the view: ‘If this letter looks as if it's addressed to me, I'm going to deal with it, even if it turns out on opening it that it was really addressed to you.’ There may be good reasons for this approach. For example, if there were excessive time costs in sending the information across to the other side for processing, it might be better to accept the somewhat inferior response because it would come quicker. The mutually inconsistent modes of processing adopted by the hemispheres create a difficulty, requiring something like an umpire for situations in which both cerebral hemispheres have access to the same information at the same time. Such ‘umpire decisions’ may be made at a very low level, below that of the hemispheres themselves, and there may be a ‘metacontrol’ switch, as far down as the brainstem, that apportions work between the hemispheres.27

From the split-brain patients, as we saw, it is clear that in the intact situation it is the will of the left hemisphere, at a more conscious level, that normally inhibits the will of the right. It would be tempting to suggest that it is also the left hemisphere, on the micro level of millisecond-to-millisecond, that takes the lion's share of the catch. Indeed some of the experimental evidence does appear to support the view that the majority of right-handed people are biased toward the mode of processing favoured by the left hemisphere, provided the stimulus is so arranged as to give them a choice.28 But other evidence is against it, and it seems that the bias probably gets in at the next level.29


So let's move up from the automatic, moment-to-moment responses of the hemispheres, to consider their relationship in the products of consciousness – at the phenomenological level, where their interaction brings into being our world of experience. At this level it is harder to demonstrate neuropsychological fact, precisely because what we are looking at is not just the interaction of neurones but the phenomenological experience of human beings. This takes place over longer periods than those of the neuronal action potential, and at the highest level of integrated awareness. No one knows where that is, if they wanted to image it, or how to measure its neurological correlates; and it is a process that fluctuates, rather than remaining still in one place at one time to be measured. What happens here has largely to be deduced from what we know of the nature, preoccupations, interests, values and typical modes of operation of the two hemispheres individually, as explored earlier in the book. But all the same some ingenious observations can be, and have been, made.

In the discussion of level one, the emphasis was on the necessary inhibition of one hemisphere by the other, since they each need to work separately. However, at a higher level, and over longer time spans, they also need to work together, not just because some important human faculties, such as imagination, appear to depend on the synthesis of the workings of both hemispheres. In the last chapter I described evidence for the primacy of the right hemisphere in constituting our experience of reality, with the need for left hemisphere ‘unfolding’ of what the right hemisphere understands, so that the now unfolded vision can subsequently be reintegrated with the reality of the right hemisphere. I expressed this in terms of Hegel's Aufhebung, the essential point being that something new, that was not present before, comes into being through the process, not negating the earlier stages, but transforming them.

And one of the most significant findings from hemisphere research at the neurological level demonstrates just that. Marie Banich, Director of the Institute of Cognitive Science at Boulder, Colorado, and a leading researcher into hemisphere interaction, writes:

The major finding to come out of our laboratory since the mid-1980s is that interhemispheric interaction is much more than just a mechanism by which one hemisphere ‘photocopies’ experiences and feelings for its partner. Interhemispheric interaction has important emergent functions – functions that cannot be derived from the simple sum of its parts …the nature of processing when both hemispheres are involved cannot be predicted from the parts.30

It is possible to determine which areas of the brain are recruited in order to carry out a task using one hemisphere only, and, by repeating it, this can be determined for each hemisphere on its own. But when both hemispheres co-operate in carrying out the task, it is not just that additional regions come into play, as one might expect, but wholly different regions altogether, many of those that were activated in the single-hemisphere condition remaining inactive, and new areas in different parts of the brain, being recruited.31

At a global level we can prefer one or the other hemisphere

But do the hemispheres actually co-operate to bring this situation about? There are some clues at the neurological level to the relationship they have in practice.

It turns out that one or other hemisphere may predominate – its particular cognitive and perceptual style as a whole more greatly influencing our experience of the world – not only during chunks of phenomenological experience (which therefore must last longer than a few milliseconds at a time) but even over very long periods. We can even have, as personalities, characteristic and consistent biases towards one or other hemisphere, certainly for particular kinds of experience, associated with differing degrees of arousal and activation in either hemisphere. This phenomenon is known as ‘hemispheric utilisation bias’ or ‘characteristic perceptual asymmetry’.32

Some interesting sidelights on the relationship between the hemispheres can be seen by examining the way in which these individual differences affect competition for the control of visual attention. In experiments where a task is carried out requiring attention to one's non-favoured visual field (the field contralateral to one's non-favoured hemisphere), while irrelevant, distracting information is presented to the favoured visual field, those subjects with a characteristic left-hemisphere bias found that the already strong tendency for the left hemisphere to prioritise the right visual field, and downplay the left visual field, was enhanced. This meant that the irrelevant information on the right interfered with the task going on in the left visual field (controlled by the right hemisphere). But for those with a characteristic right-hemisphere bias, when conditions were reversed, no such competitive effects were seen: irrelevant information in the right hemisphere's favoured left visual field did not interfere with the subject's ability to attend to the matter in hand going on, now, in the right visual field (the field favoured by the left hemisphere).33

This suggests a more even distribution of concern in the right hemisphere than in the left. We know that the right hemisphere ‘looks out’ for both hemispheres' territory, not just its own, like the left hemisphere. But this goes further: having a ‘utilisation bias’ in favour of the left hemisphere intensifies this effect, whereas having a similar bias in favour of the right hemisphere does nothing to upset the even-handedness of its concern. This resonates with another well-established research finding: that transfer of information from left hemisphere to right hemisphere takes place more slowly than transfer from right to left.34 And, be it noted, this is regardless of whether the task is by nature better suited to the right hemisphere or left hemisphere.35

Competition between the hemispheres is also revealed by the response to injury. If, following a brain injury, one temporarily disables the other (non-injured) hemisphere by, for example, transcranial magnetic stimulation, this causes an improvement in function in the damaged hemisphere.36 Similarly, if the individual should suffer a stroke in the ‘normal’, non-damaged hemisphere, the originally injured hemisphere then improves. This was observed long ago by the distinguished neurophysiologist Brown-Séquard, when he found he was able to reverse a paralysis caused by a lesion in one hemisphere of a frog by inflicting a similar lesion at the same point in the contralateral hemisphere.37 What is more, such interhemispheric competition appears yet again to be asymmetrical, with the suppressive effect of the left hemisphere on the right being greater than that of the right on the left.38

Does this remind you of anything? The finding, perhaps, that once the hemispheres are in touch via the commissures, the left hemisphere is better able to suppress the right than the right is able to suppress the left (see p. 46).

Further information comes from individuals with split brains. Though they have some handicaps, they are at an advantage in at least one respect: there are some tasks they can carry out more swiftly than normal subjects.39 For example, tasks involving focussed attention usually engage primarily the left hemisphere. But, in split-brain patients, the left hemisphere cannot so effectively inhibit the right, so that both are able to bring focussed attention (the right hemisphere can also yield focussed attention) to bear and both contribute, with the result that the task is carried out in half the time.

In some cases one can see this pattern of hemisphere competition exemplified in individual brain development following an injury. Subjects with early left-hemisphere brain damage, in whom therefore language has to be accommodated in the right hemisphere alongside the normal right-hemisphere synthetic-Gestalt faculties, show IQ deficits in their non-verbal functions, because the presence of language in the same hemisphere interferes. The direction of influence tends again to be more that of the left hemisphere over the right.

What the stories of the split-brain patients in their first few months after operation also reveal is that it is the left hemisphere, Gazzaniga's interpreter, that is in control, at the conscious level, of the consistent nature of ‘our’ experience, even though we may have differing views, desires, and values in either hemisphere. In inter-manual conflict, it is never the right hand that is experienced as the rebel, the ‘naughty’ hand, the one that is ‘out of control’: it is always the left, that pushes the other way, grabs the wheel, chooses the ‘wrong’ clothes. ‘Of course it is’, you may say: ‘it's not the right hand that behaves disruptively.’ But disruptive of what? Once the script has been written and the play half performed by the left hemisphere, an incursion from the right hemisphere is bound to be disruptive and unwelcome from its point of view. It's the left hemisphere, ignorant of what is going on in the right hemisphere, that both decides what it is that ‘I’ want, and then judges any interruption from the right hemisphere as contrary to ‘my’ best interests. But set it in another context, and who knows what might have happened had he actually listened a long while back to his right hemisphere and left his wife rather than embrace her; or – in another patient's story – had she closed the door, driven the other way, worn the flame-coloured dress? At any rate, at least we can deduce that when she says ‘I know what I want to wear’, she means ‘My left hemisphere knows what it wants me to wear, and I am identified with my left hemisphere.’40

From the previous chapter one can see that it is essential that what the left hemisphere yields is returned to the realm of the right hemisphere, where it can once again live. Only the right hemisphere is in touch with primary experience, with life; and the left hemisphere can only ever be a staging post, a processing house, along the route – not the final destination. The right hemisphere certainly needs the left, but the left hemisphere depends on the right.41 Much that marks us out, in the positive sense as well as the negative sense, as human beings requires the intervention of the left hemisphere, as long as it is acting in concert with the right hemisphere. Important human faculties depend on a synthesis of their activity. In the absence of such concerted action, the left hemisphere comes to believe its territory actually is the world.

Despite the asymmetry in their roles, in favour of the right hemisphere, there is an important opposing asymmetry of power, in favour of the left hemisphere. The Master makes himself vulnerable to the emissary, and the emissary can choose to take advantage of the situation, to ignore the Master. It seems that its nature is such that it is prone to do so, and it may even, mistakenly, see the right hemisphere's world as undoing its work, challenging its ‘supremacy’.

The image suggests, of course, that the two hemispheres have wills that may not always be in harmony. How legitimate is it to think of the hemispheres as having wills in this sense? Bogen refers to two ‘crucial facts’: that ‘it takes only one hemisphere to have a mind’, and that ‘hemispheres can sustain the activity of two separate spheres of consciousness following commissurotomy’.42 Sperry writes that, in commissurotomy patients,

each hemisphere can be shown to experience its own private sensations, percepts, thoughts, and memories that are inaccessible to awareness in the other hemisphere. Introspective verbal accounts from the vocal left hemisphere report a striking lack of awareness in this hemisphere for mental functions that have just been performed immediately before in the right hemisphere. In this respect each surgically disconnected hemisphere appears to have a mind of its own, but each cut off from, and oblivious to, conscious events in the partner hemisphere.43

And it is not just like this in surgically disconnected hemispheres. Temporary inactivation of one or other hemisphere, through the Wada test, produces similar results.

Even without such specialised procedures, sometimes the brain of the ordinary subject shows disconnection comparable to that found in split-brain subjects.44 If there are separate sensations, percepts, thoughts and memories, as well as separate ways of dealing with all of these, it would hardly be surprising if there were separate desires formed, separate wills, to each hemisphere – and we know from the split-brain subjects' experience that this is the case.

But we also know from them, as we know from our own experience of divided will, that, despite all this, there can be only one unified field of consciousness. And how is that?

Sperry makes his own attempt to answer this question, and his solution lies in referring to something that must go on at the top end of the process. He writes: ‘The overall, holistic functional effect could thus determine the conscious experience. If the functional impact of the neural activity has a unitary effect in the upper-level conscious dynamics, the subjective experience is unified.’45 In dealing with these issues it is nigh on impossible to remain within the limits of commonly accepted language use, and I make no claim to be able to solve these issues in a way that avoids the traps of language. But I cannot help finding phrases such as ‘the overall, holistic functional effect’ unsatisfactory in explanatory terms. It seems to beg every question – what is it, other than a redescription of what it is trying to explain? And in which hemisphere does it, or ‘the upper-level conscious dynamics’, whatever they may be, lie?

It seems to me more fruitful to think of consciousness not as something with sharp edges that is suddenly arrived at once one reaches the very top of mental functioning, but as a process that is gradual, rather than all-or-nothing, and begins low down in the brain, rising up from below the level of the hemispheres, before it reaches the great divide. It may be that the reverse of Sperry's model applies. The problem then becomes not how two wills can become one unified consciousness, but how one field of consciousness can accommodate two wills. These evolve from the higher cognitive levels, because it is here that different worlds are given to consciousness by each hemisphere, with different sets of values and different experiences. As I move from one situation to another, where different contexts and different sets of values change my preferences, my will changes.

Perhaps, then, consciousness is unified at the lowest levels, and it is actually only when the process becomes self-conscious at the topmost levels, within cognition, that the possibility of separation occurs. Here I would quote Jaak Panksepp:

Most forms of intentionality and deep emotional feelings are not split in any obvious way by a parting of the hemispheres. Only the cognitive interpretations [high-level phenomena] of specific events are affected …The unity of an underlying form of consciousness in split-brain individuals, perhaps their fundamental sense of self, is affirmed by the fact that the disconnected hemispheres can no more easily execute two cognitive tasks simultaneously than can the brains of normal individuals.46

The ‘fundamental sense of self’ here referred to by Panksepp, the core of the self, is affective and deep-lying: its roots lie at a level below the hemispheric divide, a level, however, with which each cognitively aware hemisphere at the highest level is still in touch. The conflicts that exist are the result of differences between the two hemispheres in high-level cognitive processing, and in most cases they become apparent only when, under special circumstances, care is taken to introduce material to one hemisphere only, and in such a way that it will have no opportunity to descend to a level of the self which can communicate via pathways below the corpus callosum. That would help explain why split-brain patients do not experience any disturbance of the sense of self. So much of our experience, and our sense of our self, comes from low down in the ‘tree’ of consciousness, below hemispheric level: ‘integration’ does not need to be achieved. All the corpus callosum has to do is to help maintain moment-to-moment independence of the hemispheres, not integration of the self. This explains why split-brain patients describe not a fragmentation of the self, but merely some difficulty inhibiting inappropriate conflicts of action.

Panksepp sees consciousness as something that begins very deep indeed, in the so-called peri-aqueductal grey matter in the midbrain, and ‘migrates’ through higher regions of the brain, especially the cingulate, temporal and frontal regions of the cortex.47 So he sees it as something that is not all or nothing, but has a continuous existence, transforming itself as it travels upwards, through the branches, to what he calls, by analogy with the forest canopy, the ‘cerebral canopy’, until in the frontal cortices it becomes high-level cognitive awareness.48 I like this image of the cerebral ‘canopy’ because it reminds us that consciousness is not a bird, as it often seems to be in the literature – hovering, detached, coming in at the top level and alighting on the brain somewhere in the frontal lobes – but a tree, its roots deep inside us. It reinforces the nature of consciousness not as an entity, but as a process.49 If, as Thomas Nagel famously put it, consciousness is that which exists ‘when there is something it is like to be that organism’,50 this identifies that the experience of consciousness is not a ‘whatness’, but a ‘howness’ – a ‘what it is like’ – a way of being which distinguishes living things, and is bound to be at least as much a characteristic of the right hemisphere (which is excluded from the process of understanding to the very degree that we are focussed on the issue and bent on analysis) as it is of the left (the hemisphere that does the focussing and analysing).51

Consciousness is not the same as inwardness, although there can be no inwardness without consciousness. To return to Patricia Churchland's statement that it is reasonable to identify the blueness of an object with its disposition to scatter electromagnetic waves preferentially at about 0.46µm,52 to see it like this, as though from the outside, excluding the ‘subjective’ experience of the colour blue – as though to get the inwardness of consciousness out of the picture – requires a very high degree of consciousness and self-consciousness. The polarity between the ‘objective’ and ‘subjective’ points of view is a creation of the left hemisphere's analytic disposition. In reality there can be neither absolutely, only a choice between a betweenness which acknowledges itself, and one which denies its own nature. By identifying blueness solely with the behaviour of electromagnetic particles one is not avoiding value, not avoiding betweenness, not avoiding one's shadow being cast across the picture. One is using the inwardness of consciousness in a very specialised way to strive to empty itself as much as possible of value, of the self. The paradoxical result is an extremely partial, fragmented version of the colour blue, which is neither value-free nor independent of the self's disposition towards its object.

One of the difficulties in practising philosophy is that we are obliged to bring into the focus of our attention, and therefore make explicit, processes which by their nature are not focussed on, and cannot be made explicit. Any attempt to do so immediately and radically alters what we find. Wittgenstein repeatedly remarks on the way that stopping acting and engaging with the world in order to reflect on it makes things appear alien – we feel ‘the phenomenon is slipping away from us’ (see p. 89 above). Thus his thrust as a philosopher is to help us get on with things, to ‘move about around things and events in the world instead of trying to delineate their essential features’53 – in other words, to be skilled participants in the life of the world as it flows (right hemisphere), not detached analysts of the process once it stops (left hemisphere). Whether this might undermine the practice of philosophy altogether is a question of which Wittgenstein was, of course, also highly aware.

This has profound implications for our attempts to pin down what consciousness is, since such attempts always and necessarily bring to bear high levels of self-awareness which induce a reflexive condition different from consciousness as understood intuitively. Panksepp, who has written on the subject from the standpoint of a neuroscientist, sees consciousness as ultimately affective in nature, and founded on ‘motor processes that generate self-consciousness by being closely linked to body image representations’ – in other words, we are first and foremost aware of ourselves through feeling states that lead to action in, and engagement with, the world as embodied beings. He rejects the view that consciousness arises from sensory-perceptual imagery, according to the prevailing cognitive model, based as it is on what we find when we stop acting in the world and introspect on our own thought processes. ‘Consciousness’, he writes, ‘is not simply a sensory-perceptual affair, a matter of mental imagery, as the contents of our mind would have us believe. It is deeply enmeshed with the brain mechanisms that automatically promote action readiness.’54

I know that it does not necessarily feel as if the sense of the self comes from lower levels of the nervous system. But I do not think it would ‘feel’ any different if it did or didn't. The problem is that when we are trying to introspect on ourselves we change the nature of what we are looking at. Our active, embodied engagement with the world is a skill. It is something we learn before we are conscious of it, and consciousness threatens to disrupt it, as it disrupts all skills. In fact what one means by a skill is something intuitive and non-explicit. We do not work out what actions we need to make in order to hammer effectively, and then give instructions consciously to our hands and arms to carry them out in a certain order, with myriads of caveats and qualifications – ‘If the hammer glances off too much to the right, aim slightly further to the left; if this does not work, try using slightly less force,’ and so on. If we did, we would hammer very badly: instead we just pick up the hammer and strike. As Dreyfus, a Heidegger scholar who has written powerfully about the problems of trying to ‘operationalise’ skills, particularly more complex skills that require considerable experience, points out, we resort to explicit analysis of the process only when we introspect on what happened – either because something has gone wrong, or because we are complete beginners. Philosophers and psychologists who champion the view that our mental processes are akin to those of a computer ‘have yet to notice that we only become aware of our skills when things are not going smoothly or when someone performing an experiment has given us a task in which we have no prior experience or skill. Then we are indeed dependent on analysis.’55

Which brings us back to the question of whether ‘consciousness is in the left hemisphere’. Obviously much depends on what is meant by ‘conscious’, and if consciousness is a continuum, it will necessarily be impossible to be clear-cut about it – in fact supposing it to be a clear-cut phenomenon would be one sign of being off track. The most robust distinction that can be made, however, although it is itself far from unproblematic, is that between self-consciousness and consciousness ‘pure and simple’. But what is consciousness without self-consciousness? We cannot tell whether another creature has self-consciousness – or, strictly, consciousness at all – so we are obliged to introspect on our own experience. However, such introspection is by definition self-conscious, and so we will not get to know what it is like to be conscious without being self-conscious by this route, either. One can however distinguish between times when one is aware of oneself as the object of attention and times when one is simply aware of being. This is the closest I can get to the distinction. It has the double advantage of coinciding with what we normally mean by ‘self-consciousness’ in everyday parlance; and of pinpointing the abnormality in subjects whose psychopathology, as in many anxiety disorders, especially social phobia, is of excessive self-consciousness. Sufferers describe an uncomfortable sense of being observed, even of there being an ‘eye’ that observes their ‘I’ (in the world of schizophrenia this process becomes psychotic, and is experienced as a reality; see Plate 1). Such self-consciousness also has the paralysing effect of rendering awkward and artificial the skills of ordinary social life which have to remain intuitive and unconscious to be effective; so one of the aspects of self-consciousness is the dragging into the centre of awareness of what should remain outside of it.

Most, if not all, of the ‘functions’ mediated by the right hemisphere fall into this category of what has to remain outside the focus of awareness – implicit, intuitive, unattended to. And so it looks as though self-consciousness, at least, comes about when the left hemisphere is engaged in inspecting the life of the right. As far as the right hemisphere activities themselves go, we are conscious most of the time when carrying them out, but we are not focussed on them, and therefore not conscious of them – the attention is somewhere else (and they can come and go from consciousness, depending on what else is going on).56 Many over-learned routines, such as driving a familiar route, are like this. At the time we are not aware of carrying them out, but we would become so immediately if our attention were drawn to it – or if we made a mistake.57 Many over-learned and routine behaviours must involve the left hemisphere. So clearly not everything in the left hemisphere can be – or ever could have been – in the focus of attention. For one thing, that focus is very small; and, for another, very little of the left hemisphere can be near the top of the cerebral canopy, where awareness mainly is.

The idea that self-consciousness, in the sense of being aware of ourselves doing or being something, is the left hemisphere inspecting the right is supported by a number of observations. The attentional ‘spotlight’, as we have seen, is a function of the left hemisphere. The casualties in self-consciousness are all right-hemisphere-based, social or empathic skills. And schizophrenic subjects, whose psychopathology depends on a reflexive hyperconsciousness, and who often depict a detached observing eye in their paintings, show a relative hypofunction of the right hemisphere in relation to the left (see Plate 2).

More specifically, the idea that things come into being through an apophatic process (see p. 197) also casts light, I believe, on the problem of the self, and helps to confirm this view. Hume introspected and found no sign of the self, just a string of sense impressions. Fichte thought that was quite natural. The self, he believed, would not emerge in cognition: the more absorbed you are in the process of attending, the less aware you are of yourself as the absorber. It is only when there is some kind of resistance that one becomes aware of the self, ‘not as an object but as that which is obtruded upon by some kind of recalcitrant reality’.58 This is as if things become, in Heidegger's terms, vorhanden, separate from us, and we feel ourselves separate from them. In Merleau-Ponty's terms, it has to do with the plane of focus: whether the ‘I’ is transparent or opaque. I come into being as a self through the experience of resistance, as a lake is bounded by the shore which makes it a lake. These associations with opacity and Vorhandenheit again suggest that the self-conscious self emerges only when the focus of left-hemisphere attention is brought to bear on the right-hemisphere world.

What about those who have suffered a left-hemisphere stroke? Clearly they remain conscious. The degree to which they remain self-conscious is harder to assess because of the difficulty of reporting on it in an articulate fashion. It is not impossible to imagine ways of circumventing this problem, however, though I am not aware of research addressing the point. I would be surprised if self-consciousness were altogether lacking, and it may be that, if the tree cannot reach the forest canopy on one side of the fence, it will push up on the other in an attempt to do so, with possibly paradoxical results that those who have had left-hemisphere strokes may be more, rather than less, self-conscious, because of the damaging effect of having the attentional spotlight in the same hemisphere as all those things that by their nature need to flee from it; rather as those with left-hemisphere brain damage in childhood develop poorer right-hemisphere skills because of the presence in the same hemisphere of language, with its Gorgon stare.

Panksepp's vision of consciousness as a process that begins in the midbrain and migrates upwards also suggests a possible approach to the so-called binding problem, which refers to the difficulty of knowing how the various modular elements of brain function come to be united in the experience of the self – where in, or by what part of, the brain do the various modules that are identified by cognitive psychology get to be unified?

One answer to this is epistemological: that this is largely a problem created by the model of mind we have espoused. Derived inevitably from the self-conscious, self-reflexive mechanisms of the left hemisphere, our examination of ourselves identifies the parts of a living whole, then wonders how the parts can be put together (the Frankenstein's monster problem). But Panksepp's vision gives a neurological answer to this problem: what look like ‘modules’ are better seen as branches of a tree – except that, in this tree, Spanish moss also hangs between the branches.

Ramachandran describes experiments which

flatly contradict the theory that the brain consists of a number of autonomous modules acting as a bucket brigade. Popularised by artificial intelligence researchers, the idea that the brain behaves like a computer, with each module performing a highly specialised job and sending its output to the next module, is widely believed …But my experiments …have taught me that this is not how the brain works. Its connections are extraordinarily labile and dynamic. Perceptions emerge as a result of reverberations of signals between different levels of the sensory hierarchy, indeed across different senses.59

Experience is not just a stitching together, at the topmost level, of Gazzaniga's ‘patchwork’ of functions. Experience is already coherent in its wholeness at very low levels in the brain, and what higher levels do is not to put together bits (left-hemisphere fashion) but to permit the growth of a unified whole (right hemisphere fashion). There are known to be highly complex, and complexly interconnected, cortico-subcortical loops involving the basal ganglia, deep-lying nuclei in the brain, way below the corpus callosum, which, as we understand more about them, we realize increasingly are involved, not just in motor co-ordination, as we used to think, but in both the segregation and the integration of motor, affective and cognitive functions. These ‘loops’ underlie subtle, emotionally laden aspects of experience. Although the cognitive, motor and affective elements are carefully segregated, even within the subthalamic nuclei – relay centres that are minute (only 5–15 mm in diameter) – they are also equally carefully interconnected (even at this very low level there is division within union). The processes that are subserved are learned, but have become nonetheless automatic, not under conscious control. Patients with conditions such as Parkinson's disease can now be treated by a procedure known as deep brain stimulation, which involves surgically implanting electrodes in the subthalamic nuclei and stimulating them for brief periods (a painless procedure that is carried out, and indeed must be carried out, with the patient fully conscious). Professor Yves Agid and his team at the Pitié-Salpêtrière in Paris found that by minute variation in the position of the electrode, they caused a patient to change from the impassive, immobile, ‘switched-off’ Parkinsonian state, to one of severe depression. In video recordings their patient can be seen grimacing, holding her head in her hands, and expressing feelings of sadness, guilt, uselessness, and hopelessness: ‘I'm falling down in my head, I no longer wish to live, to see anything, hear anything, feel anything …’ When asked why she was crying and if she felt pain, she responded: ‘No, I'm fed up with life, I've had enough …I don't want to live any more, I'm disgusted with life …Everything is useless …worthless: I'm scared in this world.’ When asked why she was sad, she replied: ‘I'm tired. I want to hide in a corner …I'm crying over myself, of course …I'm hopeless, why am I bothering you …’ Less than 90 seconds after stimulation was stopped, the depression disappeared. For the next five minutes she was in a mildly hypomanic state, laughing and joking with the examiner, and playfully pulling his tie. By moving the probe minutely, she became frankly hypomanic, appearing not just cheerful, but being ‘over the moon’, and restlessly active – all within minutes or seconds.60

Experience that is completely ‘fused’ or unified in its automatic recruitment of cognitive, emotional and motor aspects of being, and which is experienced at the highest phenomenological level as an integrated phenomenon, with thoughts about the uselessness of carrying on living, feelings of deep sadness and gestures of despair, is already coherently constituted (and ‘ready to go’) at this low level in the tree of consciousness. It is not as if moving the electrode caused incoherent experience, such as the motor restrictions of Parkinson's disease, with the cognitions of mania and the affect of depression, parts without relationship that would need to await the highest levels of cortical function for integration. Experiential wholes, that are completely coherent across all realms, and affect us at the most conscious as well as unconscious levels, are already present well below consciousness.


To recap. More than one will (and a fortiori more than one set of goals or values) does not mean more than one consciousness: so with one consciousness we can have more than one will, expressive of more than one aim. In Chapters 2 to 4, I suggested that the two hemispheres, as two vast coherent neurological systems, each capable of sustaining consciousness on their own, do have different concerns, goals and values, and that these are therefore likely to be expressed in different wills; and in this chapter I have put forward evidence suggesting that a conflict of wills may be exactly what we find. In Chapter 5, I showed that on a range of both philosophical and neuropsychological grounds the right hemisphere has primacy, and that, though the left hemisphere has a valuable role, its products need to be returned to the realm of the right hemisphere and once more integrated into a new whole, greater than the sum of its parts. Earlier in this chapter I showed that on the first, millisecond-to-millisecond, level, the most obvious fact about the relationship between the hemispheres is that it depends on separation and mutual inhibition, which is coherent with the view of the relationship between the phenomenological worlds of the two hemispheres, according to which each must, for different reasons, remain ignorant of the other. At the second level, that of their more global interaction over longer time periods that form the basis of conscious experience, the evidence is that the relationship is not symmetrical or reciprocal, with the advantage being taken by the left hemisphere.

There is therefore a conflict of asymmetries.

Ontological asymmetry

In favour of the right hemisphere there is what might be called ontological asymmetry (the primacy of the right hemisphere's interaction with whatever exists). The right hemisphere is the primary mediator of experience, from which the conceptualised, re-presented world of the left hemisphere derives, and on which it depends. Because, as Blake says, ‘Reason is the bound or outward circumference of Energy’ (energy being something like Scheler's Drang), which, as he puts it, ‘is the only Life, and comes from the Body’, the left hemisphere does not itself have life, such life as it appears to have coming from reconnecting with the body, emotion and experience through the right hemisphere. It is this primacy of the (right-hemisphere-mediated) interaction with the lived world beyond ourselves over our (left-hemisphere-mediated) re-presentation of it that lies behind Goethe's inversion of the Johannine pronouncement: ‘In the beginning was the word [logos].’ In the mouth of Faust it becomes: ‘Im Anfang war die Tat!’ (‘In the beginning was the deed’).61

Asymmetry of function

Also in favour of the right hemisphere is an asymmetry of function, which follows from the first asymmetry. In the functioning together of the two hemispheres, the products of the left hemisphere need to be returned to the realm of the right hemisphere in order to live. While experience is enriched by the opposite process, whereby the products of the right hemisphere are sent to the left hemisphere for ‘unpacking’, there is no necessity for that process. One process is literally vital: the other is not.

These two asymmetries indicate where the interhemispheric balance of power ought to lie, and indeed needs to lie: with the right hemisphere. But it does not. There are three other asymmetries which mean that in fact the balance of power is doomed to be dangerously skewed towards the lesser hemisphere, the left. These are an ‘asymmetry of means’, ‘asymmetry of structure’ and ‘asymmetry of interaction’.

Asymmetry of means

The left hemisphere point of view inevitably dominates, because it is most accessible: closest to the self-aware, self-inspecting intellect. Conscious experience is at the focus of our attention, usually therefore dominated by the left hemisphere. It benefits from an asymmetry of means. The means of argument – the three Ls, language, logic and linearity – are all ultimately under left-hemisphere control, so that the cards are heavily stacked in favour of our conscious discourse enforcing the world view re-presented in the hemisphere which speaks, the left hemisphere, rather than the world that is present to the right hemisphere. Its point of view is always easily defensible, because analytic; the difficulty lies with those who are aware that this does not exhaust the possibilities, and have nonetheless to use analytic methods to transcend analysis. It is also most easily expressible, because of language's lying in the left hemisphere: it has a voice. But the laws of non-contradiction, and of the excluded middle, which have to rule in the left hemisphere because of the way it construes the nature of the world, do not hold sway in the right hemisphere, which construes the world as inherently giving rise to what the left hemisphere calls paradox and ambiguity. This is much like the problem of the analytic versus holistic understanding of what a metaphor is: to one hemisphere a perhaps beautiful, but ultimately irrelevant, lie; to the other the only path to truth.

But even that fact, significant as it is, does not convey the true scale of the distinction, which concerns not just the functional differences at a moment in time, but what happens over much longer periods in the ordinary human brain. The left hemisphere builds systems, where the right does not. It therefore allows elaboration of its own workings over time into systematic thought which gives it permanence and solidity, and I believe these have even become instantiated in the external world around us, inevitably giving it a massive advantage (see Chapter 12). There is something very suggestive about the fact that the predominance of the left hemisphere may result from there being – possibly there having been engineered? – a deficit in the right hemisphere.

Let's look first at the way in which the two hemispheres try to know, to get a grasp on the world. Using the familiar information-processing terminology, the left hemisphere favours analytic, sequential ‘processing’, where the right hemisphere favours parallel ‘processing’ of different streams of ‘information’ simultaneously. This is what I have expressed as the left hemisphere's way of building up a picture slowly but surely, piece by piece, brick on brick. One thing is established as (apparently) certain; that forms a platform for adding the next little bit of (apparent) certainty. And so on. The right hemisphere meanwhile tries to take in all the various aspects of what it approaches at once. No part in itself precedes any other: it is more like the way a picture comes into focus – there is an ‘aha!’ moment when the whole suddenly breaks free and comes to life before us. For it, though, knowledge comes through a relationship, a betweenness, a back and forth reverberative process between itself and the Other, and is therefore never finished, never certain.

There is a huge disadvantage for the right hemisphere here. If this knowledge has to be conveyed to someone else, it is in fact essential to be able to offer (apparent) certainties: to be able to repeat the process for the other person, build it up from the bits. That kind of knowledge can be handed on, because it is not ‘my’ knowledge. It is knowledge (Wissenschaft), not knowledge (Erkenntnis). By contrast, passing on what the right hemisphere knows requires the other party already to have an understanding of it, which can be awakened in them; if they have no such knowledge, they will be easily seduced into thinking that the left hemisphere's kind of knowledge is a substitute.

Sequential analytic ‘processing’ also makes the left hemisphere the hemisphere par excellence of sequential discourse, and that gives it the most extraordinary advantage in being heard. It is like being the Berlusconi of the brain, a political heavyweight who has control of the media. Speech is possible from the right hemisphere, but it is usually very limited. We have seen that thought probably originates in the right hemisphere, but the left hemisphere has most syntax and most of the lexicon, which makes it very much the controller of the ‘word’ in general. Coupled with its preference for classification, analysis and sequential thinking, this makes it very powerful in constructing an argument. By contrast it is hard for the right hemisphere to be heard at all: what it knows is too complex, hasn't the advantage of having been carved up into pieces that can be neatly strung together, and it hasn't got a voice anyway.

Asymmetry of structure

And then there is an asymmetry of structure. There is an asymmetry inherent in this system building, namely the difficulty of escape from a self-enclosed system. The system itself closes off any possible escape mechanisms. The existence of a system of thought dependent on language automatically devalues whatever cannot be expressed in language; the process of reasoning discounts whatever cannot be reached by reasoning. In everyday life we may be willing to accept the existence of a reality beyond language or rationality, but we do so because our mind as a whole can intuit that aspects of our experience lie beyond either of these closed systems. But in its own terms there is no way that language can break out of the world language creates – except by allowing language to go beyond itself in poetry; just as in its own termsrationality cannot break out of rationality, to an awareness of the necessity of something else, something other than itself, to underwrite its existence – except by following Gödel's logic to its conclusion. Language in itself (to this extent the post-modern position is correct) can only refer to itself, and reason can only elaborate, ‘unpack’ the premises it starts with. But there can be no evidence within reason that yields the premises from which reason must begin, or that validates the process of reasoning itself – those premises, and the leap of faith in favour of reason, have to come from behind and beyond, from intuition or experience.62

Once the system is set up it operates like a hall of mirrors in which we are reflexively imprisoned. Leaps of faith from now on are strictly out of bounds. Yet it is only whatever can ‘leap’ beyond the world of language and reason that can break out of the imprisoning hall of mirrors and reconnect us with the lived world. And the evidence is that this unwillingness to allow escape is not just a passive process, an ‘involuntary’ feature of the system, but one that appears willed by the left hemisphere. The history of the last 100 years particularly, as I shall attempt to convey in Part II, contains many examples of the left hemisphere's intemperate attacks on nature, art, religion and the body, the main routes to something beyond its power. In other words its behaviour looks suspiciously tyrannical – the Master's emissary become a tyrant.

The left hemisphere, with its rational system-building, makes possible the will to action; it believes it is the one that makes things happen, even makes things live. But nothing in us, actively or positively, make things live – all we can do is permit, or not permit, life, which already exists. It may still seem difficult to understand how a set of relations that are predicated, as I would agree with Scheler (and for that matter with Heidegger) that they are, on negation – the power to say ‘no’ or not say ‘no’ – can prove to have life and be creative. It seems obvious to the left hemisphere, which is all that we have to ‘think’ (reason) with, and which remains ignorant of what the right hemisphere knows, that creation must be the result of something positive it does. It makes things, as it makes things happen, and it thinks it gives life to them. In this it is like a cat pushing a dead mouse about the floor in order to see it move. But we do not have the power to make things live: like the cat, we can only either permit life, or not permit it.

This idea is not as strange, however – or as unusual in the history of philosophy – as it may seem. The act of creation may be one of invention, not in the modern sense of the word, but in its older sense: one of discovery, of finding something that was there, but required liberation into being. The word invention used to mean discovery (Latin invenire, to find), and it is only since the seventeenth century that the word has come to take on the grandiose sense of something we make, rather than something we uncover. Un-covering, or ‘dis-covering’, has built into the very word the act of negation, of saying ‘no’ to something that conceals. It was Spinoza who first made the point that omnis determinatio est negatio – ‘all determination [in the sense of the bringing into sharper focus of anything] is negation’. And Hegel, who is here, as so often, in the forefront of modern philosophy, emphasised the creative importance of negation. But the idea is familiar to mainstream science. The Popperian criteria for truth incorporate the notion that we can never prove something to be true; all we can do is prove that the alternatives are untrue.

The feeling we have of experience happening – that even if we stop doing anything and just sit and stare, time is still passing, our bodies are changing, our senses are picking up sights and sounds, smells and tactile sensations, and so on – is an expression of the fact that life comes to us. Whatever it is out there that exists apart from us comes into contact with us as the water falls on a particular landscape. The water falls and the landscape resists. One can see a river as restlessly searching out its path across the landscape, but in fact no activity is taking place in the sense that there is no will involved. One can see the landscape as blocking the path of the water so that it has to turn another way, but again the water just falls in the way that water has to, and the landscape resists its path, in the way it has to. The result of the amorphous water and the form of the landscape is a river.

The river is not only passing across the landscape, but entering into it and changing it too, as the landscape has ‘changed’ and yet not changed the water. The landscape cannot make the river. It does not try to put a river together. It does not even say ‘yes’ to the river. It merely says ‘no’ to the water – or does not say ‘no’ to the water, and, by its not saying ‘no’ to the water, wherever it is that it does so, it allows the river to come into being. The river does not exist before the encounter. Only water exists before the encounter, and the river actually comes into being in the process of encountering the landscape, with its power to say ‘no’ or not say ‘no’. Similarly there is ‘whatever it is that exists apart from ourselves’, but ‘whatever it is that exists’ only comes to be what it is as it finds out in the encounter with ourselves what it is, and we only find out and make ourselves what we are in our encounter with ‘whatever it is that exists’.

A problem of time emerges. There is in all descriptions, that are, after all, re-presentations, the problem that they begin with something known. They then build on what is known with something else that is known. These could be words or mental images (like photographs, what the French call clichés – fixed, fragmented, two-dimensional). Thus it is that we have the illusion of something being brought into being by being put together. All language is inevitably like this: it substitutes for the experienced ambiguity and uncertainty of the original encounter with something in the process of coming into being, a sequence of apparently fixed, certain pieces of information. Information is by definition something fixed, a bunch of facts as we put it. But all the conscious mind can do when it has a bunch of pieces is put the pieces together to try to make something. However, this is no more a way of actually re-enabling the experience itself than living beings are made by stitching together the limbs. Thus the apparent sequence of things causing one another in time is an artefact of the left-hemisphere way of viewing the world. In creation we are not actively putting together something we already know, but finding something which is coming into being through our knowing, at the same time that our knowing depends on its coming into being; as Pushkin says of Evgeny Onegin, in the middle of the work itself, that he did not know where it was going, it was an unfinished path, a journey, an exploration, of whatever it was that was coming into being between himself and the imaginative world.

Asymmetry of interaction

Finally there is an asymmetry of interaction. It seems to me that the overall way in which the hemispheres relate has critically shifted from a form of what might be called stable dynamic equilibrium to an inequilibrium. When there are two necessary but mutually opposed entities in operation together, an imbalance in favour of one can, and often will, be corrected by a shift in favour of the other – a swing of the pendulum. But negative feedback can become positive feedback, and in the left hemisphere there is an inbuilt tendency for it to do so.63 To return to the image of the pendulum, it would be as if a violent swing of the pendulum shifted the whole clock, which then over-balanced. I believe that we have entered a phase of cultural history in which negative feedback between the products of action of the two hemispheres has given way to positive feedback in favour of the left hemisphere. Despite the primacy of the right hemisphere, it is the left hemisphere that has all the cards and, from this standpoint, looks set to win the game. That is the subject of Part II.

What light does Heidegger cast on the interaction of the hemispheres? According to Heidegger, what were anciently seen as the Apollonian, more rationalistic, and Dionysian, more intuitive, aspects of our being have become grossly unbalanced. Nietzsche claimed that the constant opposition between these two very different tendencies led to a fruitful incitement to further and ever higher levels of life and creativity (which accords with the evidence of the relationship between the two hemispheres at its best). War, as Heraclitus said, is the father of all things. But the war between these tendencies has become, according to Heidegger, no longer creative but merely destructive. We have become ‘pre-eminently endowed with the ability to grasp and delimit’: the Apollonian has triumphed at the expense of the Dionysian. We are caught up, he believed, in a frenzy of ‘forming projects, enclosures, frameworks, division and structuring’, destroying ourselves and our environment and turning all into ‘resource’, something to be merely exploited, Nature turned into ‘one gigantic filling station’, as he once graphically put it.64 This is the opposite of the problem the Greeks confronted, for whom the balance lay more towards the Dionysian, and who therefore strove, and needed to strive, towards the Apollonian.

However, from within Heidegger's own philosophy there emerge grounds to suppose that the situation is not beyond remedy. He quoted with approval Hölderlin's lines: Wo aber Gefahr ist, wächst / Das Rettende auch (‘Where there is danger, that which will save us also grows’). How I understand this in relation to the brain is this.

At the first level, it tells us something about the constant, relatively stable, interrelation of the hemispheres at their best. In a way it is Nietzsche's point about the fruitful relation of the Apollonian and Dionysian. Within the realm of the left hemisphere (‘where there is danger’) there is also the possibility of an ‘unfolding’ of what is implicit, which, if returned to the right hemisphere, will lead to something greater and better coming forward (‘that which will save us’). This sounds very abstract, but I think it can be made clearer by an example. If we subject a work of art, say, or even the human body, to detached, analytic attention, we lose the sense of the thing itself, and its being in all its wholeness and otherness recedes. But the result of such attention, provided it is then relinquished, so that we stand in a state of openness and receptivity before the thing once again, may be a deeper and richer ‘presencing’. The work of the left hemisphere done, the thing ‘returns’ to the right hemisphere positively enriched. The best criticism of works of art produces just this result, and the study of medicine at its best achieves it, too, in relation to the human body. Again it is the analogy of the necessary analysis carried out by the pianist in learning a piece, an analysis that must be forgotten during performance. The ‘danger’ inherent in the process is the potential arrogance of the left hemisphere, which may not allow the return: it may come to think of itself as all in all.

The left hemisphere can play a vital, irreplaceable role if only it can be restored to its rightful place, and allow itself to be readopted by the right hemisphere. The left hemisphere is a crucial part of the creative process – the unfolding of potential. Becoming is potential, and for Being to emerge from Becoming, it needs to be ‘collapsed’ into the present, as the wave function ‘collapses’ under observation, and Schrödinger's cat becomes either dead or alive – the terms on which we exist. But it needs nonetheless to hand its work back to the right hemisphere. It is only out of the unity of division and unity that a new unity comes: so unity melds with its opposite and yet becomes more itself. (It is not, per contra, true that out of the unity of division and unity a new division comes, nor is it true that out of the division of unity and division a new division comes: by remaining divided nothing new comes at all.)

At the second level, it has something to say about the particular danger of the modern world view, in which the hemispheres are, I believe, out of kilter. A state of fallenness, which Heidegger called Verfallen, is according to him an inevitable part of existence. But there is a sense in which, as Heidegger believed, this has its positive too, since the very existence of Verfallen prompts Dasein to awareness of the loss of its authentic self, and to strive harder towards what is authentic. This process is inevitably one of cycles or alternations of direction. The sense of longing and striving for something beyond, which otherwise we could not achieve, is an idea I will return to in Part II, where I will consider the influence of the divided brain on Western culture. In the unfolding story I tell, the left hemisphere comes to be more and more powerful: at the same time problems grow.


Right from his twenties until his death, in the year 1832, at the age of eighty-two, Goethe was obsessed with the legend of Faustus, and worked on what was to become his ultimate epic masterpiece, the long dramatic poem Faust, all his life. The legend of Faustus, the learned doctor who, frustrated by the bounds of his knowledge and power, makes a pact with the devil to increase them without limit while he lives, the price of which is his immortal soul, lies deep in the German psyche, and versions of the story go back to the Middle Ages. The myth is clearly a warning against hubris. In Goethe's version of the story, Faust is an essentially good man, who has already done much for others through his skills as a physician, before his lust for power and knowledge lead him to do many destructive things. Yet, although Faust comes in the end to realise that there are indeed limits to what humanity can understand or achieve, he is brought back, through his own pain and remorse, to an awareness of the good his knowledge can bring to others: his ultimate moment of happiness, the purpose of his bargain with Mephistopheles, comes through his realisation of what he can do for humanity, not for himself. At the end of the work, God, not the devil, takes his soul; in doing so he acknowledges the truly great value of Faust's endless striving. In this version of the myth, it seems to me, the right hemisphere's desire for understanding something further and beyond and the left hemisphere's means for helping achieve that end – the Master and his emissary working in concert – are seen as ultimately redeemed and redeeming.65 More explicitly Goethe wrote in midlife a poem, Der Zauberlehrling (The Sorcerer's Apprentice), the story of which is familiar to most people from Disney's Fantasia, but in which the returning sorcerer – to whom Goethe refers as der alte Meister, the old master – is not angry with the foolish apprentice who thought he could do on his own what his master did, but merely bids him understand that he, the Master, alone can conjure spirits safely. If the left hemisphere is hot-headed and rivalrous, the right hemisphere is not: it has an accurate appreciation of what its companion can offer.

But in either story – that of Faust or of the apprentice – there is a saving awareness that things have gone badly wrong. In the story I am to tell, the left hemisphere acts like a sorcerer's apprentice that is blithely unaware that he is about to drown, a Faust that has no insight into his errors and the destruction they have brought about.

Let us remind ourselves of the neurological literature for a moment. Although the left hemisphere does not see and cannot understand what the right hemisphere understands, it is expert at pretending that it does, at finding quite plausible, but bogus, explanations for the evidence that does not fit its version of events. It will be remembered from the experiments of Deglin and Kinsbourne that the left hemisphere would rather believe authority, ‘what it says on this piece of paper’, than the evidence of its own senses. And remember how it is willing to deny a paralysed limb, even when it is confronted with indisputable evidence? Ramachandran puts the problem with his customary vividness:

In the most extreme cases, a patient will not only deny that the arm (or leg) is paralysed, but assert that the arm lying in the bed next to him, his own paralysed arm, doesn't belong to him! There's an unbridled willingness to accept absurd ideas.

But when the damage is to the left hemisphere (and the sufferer is therefore depending on the right hemisphere), with paralysis on the body's right side,

they almost never experience denial. Why not? They are as disabled and frustrated as people with right hemisphere damage, and presumably there is as much ‘need’ for psychological defence, but in fact they are not only aware of the paralysis, but constantly talk about it …It is the vehemence of the denial – not a mere indifference to paralysis – that cries out for an explanation.66

Again Nietzsche had the measure of it: ‘“I have done that”, says my [veridical episodic right-hemisphere] memory. “I cannot have done that”—says my pride [theory-driven, denial-prone left-hemisphere], and remains adamant. At last—memory yields.’67

The left hemisphere is not keen on taking responsibility. If the defect might reflect on the self, it does not like to accept it. But if something or someone else can be made to take responsibility – if it is a ‘victim’ of someone else's wrongdoing, in other words – it is prepared to do so. Ramachandran carried out an experiment in which a patient with denial of a left arm paralysis received an injection of harmless salt water that she was told would ‘paralyse’ her (in reality already paralysed) left arm. Once her left hemisphere had someone else to blame for it, it was prepared to accept the existence of the paralysis.68

Ramachandran again: ‘The left hemisphere is a conformist, largely indifferent to discrepancies, whereas the right hemisphere is the opposite: highly sensitive to perturbation.’69 Denial, a tendency to conformism, a willingness to disregard the evidence, a habit of ducking responsibility, a blindness to mere experience in the face of the overwhelming evidence of theory: these might sound ominously familiar to observers of contemporary Western life.

A sort of stuffing of the ears with sealing wax appears to be part of the normal left-hemisphere mode. It does not want to hear what it takes to be the siren songs of the right hemisphere, recalling it to what has every right – indeed, a greater right, as I have argued – to be called reality. It is as though, blindly, the left hemisphere pushes on, always along the same track. Evidence of failure does not mean that we are going in the wrong direction, only that we have not gone far enough in the direction we are already headed.

The left hemisphere as a sleepwalker

The popular assumption, aided by the reflections of some respectable neuroscientists, is that the right hemisphere might be something like a zombie, or a sleepwalker. It seems to be supposed naïvely that the defining quality of the zombie, that quintessentially uncanny phenomenon, is the lack of the verbalising and rationalising intelligence exemplified by the left hemisphere.

In Chapter 10 I will deal with the phenomenon of the uncanny, of the zombie and its like, phenomena that started to figure in literature, oddly but significantly enough, in the Enlightenment. I will suggest that the uncanny looks extraordinarily like certain aspects of the world according to the left hemisphere, in which vitality is absent, and the human is forced to approximate to the mechanical. Zombies have much in common with Frankenstein's monster, after all. They perform like computer simulations of the human. There is no life in their eyes. And Giovanni Stanghellini has explored with subtlety, in his book Disembodied Spirits and Deanimated Bodies, the way in which the ‘zombie’ state is mimicked by schizophrenia, a largely right-hemisphere-deficit condition.70

So-called ‘zombie’ states are characterised by dissociation, in which the conscious mind appears cut off from the body and from feeling. That in itself suggests a relative hypofunction of the right hemisphere. Dissociation is, furthermore, the fragmentation of what should be experienced as a whole – the mental separation of components of experience that would ordinarily be processed together, again suggesting a right-hemisphere problem. Core features of dissociation include amnesia for autobiographical information, identity disturbances, depersonalisation and derealisation (lack of the sense of the reality of the phenomenal world, which appears to be a two-dimensional projection). On first principles one would therefore expect this to be a right-hemisphere-deficit condition. And subjects with right-hemisphere damage do in fact report exactly this – a change in, and a foreignness of, the self, which is disconnected from the world, a loss of feeling of belonging in the world. At times they report having become insensible automata, puppets, or mere spectators, devoid of feelings and cut off from the surrounding world (one even reported that her head has been turned into a cone, but with the front part missing; other patients reported feeling themselves to be just a casing, or cover, their ‘I’ having been separated from them, located outside the body, somewhere nearby and to the left). Subjects almost invariably speak of ‘going to another space or place’.71

Given all this, it would be extraordinary if dissociation in ‘normal’ subjects did not involve a disconnection from the right hemisphere, and an interhemispheric imbalance in favour of the left. And this is just what the empirical evidence shows.72 In fact in dissociation, the hemispheres are more than usually disengaged, with an effective ‘functional commissurotomy’, or disruption of functioning in the corpus callosum.73 Activation of the left hemisphere in subjects especially prone to dissociation results in faster than usual inhibition of the right hemisphere, whereas those not prone to dissociation exhibit a balanced interhemispheric inhibition, corroborating the idea that dissociation involves a functional superiority of the left hemisphere over the right hemisphere.74

The ultimately dissociative state is hypnosis. Despite popular prejudice that hypnosis is likely to involve the ‘release’ of the right hemisphere, it has none of the features that one would expect if it really were a state of right-hemisphere predominance. And indeed many imaging studies have now confirmed that there appears to be a predominance of left-sided activation during hypnosis.75 Being asked to imagine that a brightly coloured picture is black and white, and being hypnotised, so that we really come to believe that the picture is black and white, involve different brain states; and the difference is that, in the hypnotic state, there is abnormally increased activation in the left hemisphere.76 In hypnosis the right hemisphere is not activated, even during a typically ‘right-hemisphere’ task, using overall EEG power as the criterion.77 In a neuroimaging study exploring the neural correlates of hypnosis, activity decreases in the precuneus, posterior cingulate and right inferior parietal lobule,78 which is coherent, since as we saw earlier, in Chapter 2, these areas are known to be associated with the sense of individual agency.79 Furthermore, hypnosis produces an enhancement in focal concentration, together with a relative suspension of peripheral awareness, a mode of attention typical of the left hemisphere. It is, according to one source, ‘analogous to macular vision: intense and detailed, but restricted’, a perfect description of the left hemisphere field of vision.80 And in keeping with the left-hemisphere hypothesis, more hypnotisable subjects display higher levels of dopaminergic activity (dopamine transmission is more extensive in the left hemisphere).81

So if I am right, that the story of the Western world is one of increasing left-hemisphere domination, we would not expect insight to be the key note. Instead we would expect a sort of insouciant optimism, the sleepwalker whistling a happy tune as he ambles towards the abyss.

I now want to turn to the influence of the divided brain on Western culture.