Truth Is Not Mere Coherence
On Iain McGilchrist’s “The Master and His Emissary”
The Tao which can be expressed in words is not the eternal Tao; the name which can be uttered is not its eternal name. Without a name, it is the Beginning of Heaven and Earth; with a name, it is the Mother of all things.
— Laozi, Tao Te Ching (Lionel Giles translation)
The sorites paradox goes as follows: a grain of sand is not a heap, and adding just one more grain to it won’t turn it into one. But if, one by one, we add thousands of grains of sand, we will eventually get a heap of sand. So if adding one grain of sand doesn’t turn something that isn’t a heap into a heap, at which point do we get a heap?
In The Master and His Emissary, Iain McGilchrist puts forward the idea that the above paradox—as well as others like it—are the result of the brain’s left hemisphere’s particular way of viewing the world.1 One thing it does is divide everything in the world into parts, each of which is, in turn, composed of other parts. Another thing it does is set clear boundaries between things: something is either this or that, but not both. It tells things apart. Combined, the idea of the heap thus means something that is composed of individual grains of sand, and it must either be a heap, or not a heap. Hence the paradox—a product of a particular mode of seeing the world rather than an inherent problem of logic.
In contrast, the right hemisphere doesn’t divide things. Whereas “the left hemisphere tends to deal more with pieces of information in isolation,” writes McGilchrist, the right hemisphere deals “with the entity as a whole.” Take the famous example of the Gestalt effect below (Figure 1). At first, the image looks like some splattered blobs of black paint. But the moment the eye (or rather, the brain) connects a few of the spots, a pattern begins to rapidly reveal itself, and an image of a Dalmatian dog sniffing the ground instantly comes together. The right hemisphere integrates a jumble of black spots into something meaningful. This cannot be done by examining each spot individually—the whole must be observed at once.
The reason why the brain is divided into two hemispheres is not to have a spare extra half should something happen to one of them, but to have multiple ways of viewing the world. Imagine an eagle gliding high up in the sky. Its eye is taking in everything at once as it observes the ground below. This is the domain of the right hemisphere, which watches the world as a whole. When the eagle spots its prey, however, it will focus all its attention on it, and will maintain this attention as it swoops down to catch it. This is the function of the left hemisphere, which allows the brain to separate individual objects from the world so that it can recognize them, focus on them and act on them. Both types of attention, one open and broad, the other narrow and precise, work together to expand our range of perception.
Attention, however, “is not just another ‘function’ alongside other cognitive functions,” writes McGilchrist. “The kind of attention we bring to bear on the world changes the nature of the world we attend to.” The differences in the two hemispheres give rise to two different worlds, two “fundamentally opposed realities.” Whereas the right hemisphere gives rise to “the live, complex, embodied world of individual, always unique beings, forever in flux, a net of interdependencies, forming and reforming wholes, a world with which we are deeply connected,” the left hemisphere is a “‘re-presented’ version of it, containing now static, separable, bounded, but essentially fragmented entities, grouped into classes, on which predictions can be based.” “These are not different ways of thinking about the world,” writes McGilchrist, “they are different ways of being in the world.”
McGilchrist’s grand theory is that the history of Western culture has been shaped by a kind of power struggle between the two hemispheres, that is, by one hemisphere asserting its own reality, its own way of “being in the world,” over the other. He suggests that the West has gone back and forth between periods when the two hemispheres were more or less balanced, such as the time of Classical Greece and the Renaissance, and when the left hemisphere was more dominant than the right, such as the time of the Enlightenment and the Industrial Revolution. There are no clear right-hemisphere dominant periods because the left tends to assert itself more than the right. One reason for this is that information flow from the left to the right hemisphere is slower than the other way round. Whereas the right hemisphere always shares information with the left, the left sometimes chooses to exclude the right. But an even bigger reason for left-hemisphere dominance is the special role it plays in the development of human civilization.2
The left hemisphere’s ability to separate things from the world allows it to turn them into mental constructs, into ideas. By abstracting things from the world, the left hemisphere can reason about them as individual entities. It can think about them, theorize about them and make conclusions about them. This is the foundation of language and logic, two of the most important pillars of civilization. The right hemisphere, by contrast, cannot even speak. This alone makes the left hemisphere feel a vast sense of superiority over the right. The right hemisphere has consequently been demoted in importance, dismissed as the “silent” or “minor” hemisphere (the left, naturally, becoming the “dominant” hemisphere) and reduced in popular understanding to the domain of emotions and art (which isn’t even half right, as emotions like anger are associated with the left hemisphere).
McGilchrist spends half the book contrasting the influences of the two hemispheres on Western culture, but here is one striking example that is to do with the way churches were arranged before and after the Reformation. They added pews. Before the Reformation, the congregation would stand together in one big mass—a living, flowing crowd of people. After the Reformation, the congregation was made to sit still in neat rows of benches—it was immobilized, made to listen to the voice coming from the raised pulpit above. If McGilchrist is right about the influence of the two hemispheres, then what we see here is the left hemisphere ordering the outside world by creating frameworks and boundaries to mold it in its own image. And, by externalizing itself, by manifesting its thought patterns in the world, the left hemisphere in turn reinforces those patterns in the minds of the people inhabiting that world.
McGilchrist suggests that today the West is dominated by the left hemisphere, and is only moving further leftwards. This imbalance not only costs us our full range of mental perception, it also makes us vulnerable to the left hemisphere’s peculiar pitfalls.
One problem with the left hemisphere is that it makes stuff up. Not only does it make stuff up, it does so rapidly and seemingly without realizing it. Similarly to how the right hemisphere is able to perceive the Gestalt effect between the things it sees, the left hemisphere can combine words to construct convincing logical explanations for things it doesn’t really know about, but which sound plausible (which is, incidentally, curiously similar to how large language models work).
There’s a famous experiment by Gazzaniga and LeDoux involving a split-brain patient. His bridge between the two hemispheres, the corpus callosum, had been cut in an attempt to cure epilepsy (it worked). As it turns out, people can still function with the two hemispheres split. The way our nerves are wired is that our left hand and eye are linked to the right hemisphere, and the right hand and eye to the left—that is, to their opposite side. When we look through the right eye or grab something with the right hand, we are typically relying on the left hemisphere, and vice versa. When the hemispheres are connected, our actions are coordinated—i.e. both hands do what the brain decides as a whole. In a split-brain patient, the unity between the two hemispheres no longer exists, so, for example, whatever the right eye sees is processed only by the left hemisphere.
This allowed the experimenters to project an image to either the patient’s left or right hemisphere independently. They then showed the patient a series of picture cards and asked him to point, with either hand, to a card connected to the image he had just seen (pointing is important because the right hemisphere cannot speak). So, for example, when a snow scene was shown to his right hemisphere, the patient pointed with his left hand to the card with a picture of a shovel. Because his left hemisphere saw nothing, his right hand pointed at a random card. This makes sense. The really curious thing happened when the experimenters showed him two different images at once, one to each hemisphere.
The right hemisphere was again shown a picture of snow, while the left hemisphere was shown a picture of a chicken claw. The patient’s left hand (governed by the right hemisphere) again pointed to the card with a shovel, while the right hand (governed by the left hemisphere) pointed to the card with a chicken. Asked why he chose the shovel, the patient, “without batting an eye,” explained that he saw a chicken, and he pointed to the shovel because “you need that to clean out the chicken shed.” His left hemisphere, which did not see the image of snow, nor chose the shovel, decided to make up a plausible answer on the spot. As McGilchrist puts it, the left hemisphere is like “the sort of person who, when asked for directions, prefers to make something up rather than admit to not knowing.”
Worse still, the left hemisphere “tends towards a slavish following of the internal logic of the situation, even if this is in contravention of everything experience tells us.” As long as a conclusion is logically sound, the left hemisphere is ready to accept it in isolation from everything it knows. In an experiment by Deglin and Kinsbourne, in which one of the hemispheres was temporarily suppressed using electro-convulsive therapy, subjects were asked to judge the following:
Major premise: all monkeys climb trees;
Minor premise: the porcupine is a monkey;
Implied conclusion: the porcupine climbs trees.3
When asked if the conclusion is true, the subject whose right hemisphere was suppressed replied that it is: “the porcupine climbs trees since it is a monkey.” Asked if the porcupine is a monkey, they replied that they don’t know, but they accept it because “that’s what is written on the card.” When the experiment was performed again with same person, but this time with their left hemisphere suppressed instead of the right, the results were reversed. The conclusion is false, said the subject—the porcupine doesn’t climb trees because “it’s not a monkey.” Asked if the conclusion makes sense from the stated premises, the person stood their ground, insisting that “the porcupine is not a monkey!” “For the right hemisphere,” writes McGilchrist, “truth is not mere coherence, but correspondence with something other than itself.”
“As soon as logic as a movement of thought—and not as a necessary control of thinking—is applied to an idea,” writes Hannah Arendt in The Origins of Totalitarianism, the “idea is transformed into a premise,” from which one can draw conclusions “in the manner of mere argumentation.” This is exactly what is happening in the experiment above. The left hemisphere shifts attention to the logical coherence of the argument—whether or not every part of it is consistent—and away from the original premise upon which it is built—whether or not it reflects something real in the first place. The very nature of truth shifts to logical coherence, which makes it possible to arrive at any conclusion so long as the argument is consistent. As one 20th century tyrant said in one of his speeches, the process of logic is “like a mighty tentacle,” which “seizes you on all sides as in a vise and from whose grip you are powerless to tear yourself away; you must either surrender or make up your mind to utter defeat.”4
“The madman,” wrote G. K. Chesterton, “is not the man who has lost his reason. The madman is the man who has lost everything except his reason.”5 The madman can and will construct a wholly logical explanation for his own delusions, and will believe those delusions all the more because he has made them logical. Rather than using logic as “a necessary control of thinking,” the madman uses logic as a way to rationalize his his deluded perspective on the world, that is, he begins with a false premise and explains everything in relation to that premise. The result is that every argument he uses to support his delusion makes perfect sense, but he cannot see that they all stand on a false foundation because, being so obsessed with the details, he cannot step back and observe how it all fits—or rather, does not fit—into a greater whole.
If McGilchrist is right about hemisphere effects on culture and the shifts in their balance over time, then, besides its impact on science and art, a left-hemisphere dominated period is especially susceptible to ideological capture. The left hemisphere is ready to come up with explanations for things it has already decided to be the case, and to believe those explanations merely because they are logical. In such a world, truth becomes synonymous with logicality, and every argument, however deluded, can be made logical. That’s not to say that logic precedes irrational desire. It is, rather, like the case of Chesterton’s madman: one begins with base desires and then wraps them in logicality to produce an illusion of rationality.
But thinking spans beyond language and logic. As McGilchrist explains, thought can point at something real in the world without precisely defining it. The right hemisphere knows what a heap of sand is without counting the individual grains. Metaphor is the best example of this since the thing it conveys transcends the words used to convey it. If the whole of thought is reduced to language, the whole of thought can be reduced to logicality. To maintain its connection with reality, thought must be rooted in something beyond the words used to express it. It is said that Odin sacrificed one of his eyes to drink from the wellspring of Mímir—a source of wisdom—giving up material vision for the spiritual. In an ironic inversion, our left-brained world seems to be sacrificing one of its eyes not for wisdom, but for the narrow depthlessness of monocular sight.
Just like right and left handedness, there is a similar variation in human hemisphere functions. The labels left and right in this article refer to the hemisphere function in the majority population, but the sides can be flipped without changing their nature (in about 5% of the population, though McGilchrist notes that there exist cases with a different organization altogether).
Oswald Spengler’s “thought of the eye,” and “thought of the hand,” deserves a mention here, which I covered previously: “The eye seeks out cause and effect; the hand works on the principle of means and end. The question of whether something is suitable or unsuitable—the criterion of the doer—has nothing to do with that of true and false, the values of the observer. And an aim is a fact, while a connection of cause and effect is a truth.” While this doesn’t precisely map onto McGilchrist’s notion of how the two hemispheres work, there is considerable overlap. Moreover, Spengler identified the profound influence of the “thought of the hand” over the Western mind, in which alone “every theory is also from the outset a working hypothesis.”
The experimenters actually made a mistake here in choosing porcupines, as some porcupine species are very adept at climbing trees. But, be as it may, since neither the experimenters nor the participants seemed to be aware of the fact, their ignorance should not affect the finding.
From Stalin’s speech of January 28, 1924, quoted in Hannah Arendt’s The Origins of Totalitarianism (ch. 13).
G. K. Chesterton, Orthodoxy, (ch. 2).