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“We know nothing about the intrinsic quality of physical events,” he wrote, “except when these are mental events that we directly experience.”

I think Russell is right: Human conscious experience is wholly a matter of physical goings-on in the body and in particular the brain. But why does he say that we know nothing about the intrinsic quality of physical events except when these are mental events we directly experience? Isn’t he exaggerating? I don’t think so

I need to try to reply to those (they’re probably philosophers) who doubt that we really know what conscious experience is.The reply is simple. We know what conscious experience is because the having is the knowing: Having conscious experience is knowing what it is. You don’t have to think about it (it’s really much better not to). You just have to have it. It’s true that people can make all sorts of mistakes about what is going on when they have experience, but none of them threaten the fundamental sense in which we know exactly what experience is just in having it.

If someone continues to ask what it is, one good reply (although Wittgenstein disapproved of it) is “you know what it is like from your own case.” Ned Block replies by adapting the response Louis Armstrong reportedly gave to someone who asked him what jazz was: “If you gotta ask, you ain’t never going to know.”

So we all know what consciousness is. Once we’re clear on this we can try to go further, for consciousness does of course raise a hard problem. The problem arises from the fact that we accept that consciousness is wholly a matter of physical goings-on, but can’t see how this can be so. We examine the brain in ever greater detail, using increasingly powerful techniques like fMRI, and we observe extraordinarily complex neuroelectrochemical goings-on, but we can’t even begin to understand how these goings-on can be (or give rise to) conscious experiences.

1966 movie “Fantastic Voyage,” or imagine the ultimate brain scanner. Leibniz continued, “Suppose we do: visiting its insides, we will never find anything but parts pushing each other — never anything that could explain a conscious state.”

His mistake is to go further, and conclude that physical goings-on can’t possibly be conscious goings-on. Many make the same mistake today — the Very Large Mistake (as Winnie-the-Pooh might put it) of thinking that we know enough about the nature of physical stuff to know that conscious experience can’t be physical. We don’t. We don’t know the intrinsic nature of physical stuff, except — Russell again — insofar as we know it simply through having a conscious experience.

We find this idea extremely difficult because we’re so very deeply committed to the belief that we know more about the physical than we do, and (in particular) know enough to know that consciousness can’t be physical. We don’t see that the hard problem is not what consciousness is, it’s what matter is — what the physical is.

This point about the limits on what physics can tell us is rock solid, and it arises before we begin to consider any of the deep problems of understanding that arise within physics — problems with “dark matter” or “dark energy,” for example — or with reconciling quantum mechanics and general relativity theory.

Those who make the Very Large Mistake (of thinking they know enough about the nature of the physical to know that consciousness can’t be physical) tend to split into two groups. Members of the first group remain unshaken in their belief that consciousness exists, and conclude that there must be some sort of nonphysical stuff: They tend to become “dualists.” Members of the second group, passionately committed to the idea that everything is physical, make the most extraordinary move that has ever been made in the history of human thought. They deny the existence of consciousness: They become “eliminativists.”

no one has to react in either of these ways. All they have to do is grasp the fundamental respect in which we don’t know the intrinsic nature of physical stuff in spite of all that physics tells us. In particular, we don’t know anything about the physical that gives us good reason to think that consciousness can’t be wholly physical. It’s worth adding that one can fully accept this even if one is unwilling to agree with Russell that in having conscious experience we thereby know something about the intrinsic nature of physical reality.

It’s not the physics picture of matter that’s the problem; it’s the ordinary everyday picture of matter. It’s ironic that the people who are most likely to doubt or deny the existence of consciousness (on the ground that everything is physical, and that consciousness can’t possibly be physical) are also those who are most insistent on the primacy of science, because it is precisely science that makes the key point shine most brightly: the point that there is a fundamental respect in which ultimate intrinsic nature of the stuff of the universe is unknown to us — except insofar as it is consciousness.

Even before the evolution of a central brain, nervous systems took advantage of a simple computing trick: competition.

It coordinates something called overt attention – aiming the satellite dishes of the eyes, ears, and nose toward anything important.

Selective enhancement therefore probably evolved sometime between hydras and arthropods—between about 700 and 600 million years ago, close to the beginning of complex, multicellular life

The next evolutionary advance was a centralized controller for attention that could coordinate among all senses. In many animals, that central controller is a brain area called the tectum

At any moment only a few neurons win that intense competition, their signals rising up above the noise and impacting the animal’s behavior. This process is called selective signal enhancement, and without it, a nervous system can do almost nothing.

All vertebrates—fish, reptiles, birds, and mammals—have a tectum. Even lampreys have one, and they appeared so early in evolution that they don’t even have a lower jaw. But as far as anyone knows, the tectum is absent from all invertebrates

According to fossil and genetic evidence, vertebrates evolved around 520 million years ago. The tectum and the central control of attention probably evolved around then, during the so-called Cambrian Explosion when vertebrates were tiny wriggling creatures competing with a vast range of invertebrates in the sea.

The tectum is a beautiful piece of engineering. To control the head and the eyes efficiently, it constructs something called an internal model, a feature well known to engineers. An internal model is a simulation that keeps track of whatever is being controlled and allows for predictions and planning.

The tectum’s internal model is a set of information encoded in the complex pattern of activity of the neurons. That information simulates the current state of the eyes, head, and other major body parts, making predictions about how these body parts will move next and about the consequences of their movement

In fish and amphibians, the tectum is the pinnacle of sophistication and the largest part of the brain. A frog has a pretty good simulation of itself.

With the evolution of reptiles around 350 to 300 million years ago, a new brain structure began to emerge – the wulst. Birds inherited a wulst from their reptile ancestors. Mammals did too, but our version is usually called the cerebral cortex and has expanded enormously

The cortex also takes in sensory signals and coordinates movement, but it has a more flexible repertoire. Depending on context, you might look toward, look away, make a sound, do a dance, or simply store the sensory event in memory in case the information is useful for the future.

The most important difference between the cortex and the tectum may be the kind of attention they control. The tectum is the master of overt attention—pointing the sensory apparatus toward anything important. The cortex ups the ante with something called covert attention. You don’t need to look directly at something to covertly attend to it. Even if you’ve turned your back on an object, your cortex can still focus its processing resources on it

The cortex needs to control that virtual movement, and therefore like any efficient controller it needs an internal model. Unlike the tectum, which models concrete objects like the eyes and the head, the cortex must model something much more abstract. According to the AST, it does so by constructing an attention schema—a constantly updated set of information that describes what covert attention is doing moment-by-moment and what its consequences are

Covert attention isn’t intangible. It has a physical basis, but that physical basis lies in the microscopic details of neurons, synapses, and signals. The brain has no need to know those details. The attention schema is therefore strategically vague. It depicts covert attention in a physically incoherent way, as a non-physical essence

this, according to the theory, is the origin of consciousness. We say we have consciousness because deep in the brain, something quite primitive is computing that semi-magical self-description.

I’m reminded of Teddy Roosevelt’s famous quote, “Do what you can with what you have where you are.” Evolution is the master of that kind of opportunism. Fins become feet. Gill arches become jaws. And self-models become models of others. In the AST, the attention schema first evolved as a model of one’s own covert attention. But once the basic mechanism was in place, according to the theory, it was further adapted to model the attentional states of others, to allow for social prediction. Not only could the brain attribute consciousness to itself, it began to attribute consciousness to others.

In the AST’s evolutionary story, social cognition begins to ramp up shortly after the reptilian wulst evolved. Crocodiles may not be the most socially complex creatures on earth, but they live in large communities, care for their young, and can make loyal if somewhat dangerous pets.

If AST is correct, 300 million years of reptilian, avian, and mammalian evolution have allowed the self-model and the social model to evolve in tandem, each influencing the other. We understand other people by projecting ourselves onto them. But we also understand ourselves by considering the way other people might see us.

t the cortical networks in the human brain that allow us to attribute consciousness to others overlap extensively with the networks that construct our own sense of consciousness.

Language is perhaps the most recent big leap in the evolution of consciousness. Nobody knows when human language first evolved. Certainly we had it by 70 thousand years ago when people began to disperse around the world, since all dispersed groups have a sophisticated language. The relationship between language and consciousness is often debated, but we can be sure of at least this much: once we developed language, we could talk about consciousness and compare notes

Maybe partly because of language and culture, humans have a hair-trigger tendency to attribute consciousness to everything around us. We attribute consciousness to characters in a story, puppets and dolls, storms, rivers, empty spaces, ghosts and gods. Justin Barrett called it the Hyperactive Agency Detection Device, or HADD

the HADD goes way beyond detecting predators. It’s a consequence of our hyper-social nature. Evolution turned up the amplitude on our tendency to model others and now we’re supremely attuned to each other’s mind states. It gives us our adaptive edge. The inevitable side effect is the detection of false positives, or ghosts.

there’s that exquisite verse, one of the most beautiful in the Bible, the one that says if God cares deeply about sparrows, don’t you think He cares about you? One is so accustomed to dwelling on the second, human, half of the equation, the comforting part, but when you put your hand over that and consider only the first, it’s a little startling: God cares deeply about the sparrows. Not just that, He cares about them individually. “Are not five sparrows sold for two pennies?” Jesus says. “Yet not one of them is forgotten in God’s sight.”

The modern conversation on animal consciousness proceeds, with the rest of the Enlightenment, from the mind of René Descartes, whose take on animals was vividly (and approvingly) paraphrased by the French philosopher Nicolas Malebranche: they “eat without pleasure, cry without pain, grow without knowing it; they desire nothing, fear nothing, know nothing.” Descartes’ term for them was automata

In On the Origin of Species, Charles Darwin made the intriguing claim that among the naturalists he knew it was consistently the case that the better a researcher got to know a certain species, the more each individual animal’s actions appeared attributable to “reason and the less to unlearnt instinct.” The more you knew, the more you suspected that they were rational. That marks an important pivot, that thought, insofar as it took place in the mind of someone devoted to extremely close and meticulous study of living animals, a mind that had trained itself not to sentimentalize.

The sheer number and variety of experiments carried out in the twentieth century—and with, if anything, a renewed intensity in the twenty-first—exceeds summary. Reasoning, language, neurology, the science of emotions—every chamber where “consciousness” is thought to hide has been probed. Birds and chimps and dolphins have been made to look at themselves in mirrors—to observe whether, on the basis of what they see, they groom or preen (a measure, if somewhat arbitrary, of self-awareness). Dolphins have been found to grieve. Primates have learned symbolic or sign languages and then been interrogated with them. Their answers show thinking but have proved stubbornly open to interpretation on the issue of “consciousness,” with critics warning, as always, about the dangers of anthropomorphism, animal-rights bias, etc.

If we put aside the self-awareness standard—and really, how arbitrary and arrogant is that, to take the attribute of consciousness we happen to possess over all creatures and set it atop the hierarchy, proclaiming it the very definition of consciousness (Georg Christoph Lichtenberg wrote something wise in his notebooks, to the effect of: only a man can draw a self-portrait, but only a man wants to)—it becomes possible to say at least the following: the overwhelming tendency of all this scientific work, of its results, has been toward more consciousness. More species having it, and species having more of it than assumed.

The animal kingdom is symphonic with mental activity, and of its millions of wavelengths, we’re born able to understand the minutest sliver. The least we can do is have a proper respect for our ignorance.

The philosopher Thomas Nagel wrote an essay in 1974 titled, “What Is It Like To Be a Bat?”, in which he put forward perhaps the least overweening, most useful definition of “animal consciousness” ever written, one that channels Spinoza’s phrase about “that nature belonging to him wherein he has his being.” Animal consciousness occurs, Nagel wrote, when “there is something that it is to be that organism—something it is like for the organism.” The strangeness of his syntax carries the genuine texture of the problem. We’ll probably never be able to step far enough outside of our species-reality to say much about what is going on with them, beyond saying how like or unlike us they are. Many things are conscious on the earth, and we are one, and our consciousness feels like this; one of the things it causes us to do is doubt the existence of the consciousness of the other millions of species. But it also allows us to imagine a time when we might stop doing that.

The purpose of the surgery was to remove electrodes that had previously been implanted in the patients’ brains to monitor seizures. But before they were taken out, the electrodes enabled the researchers to study the activity of individual neurons in the cortex, in addition to large-scale brain activity from EEG recordings.

importance of communication between discrete groups of neurons, both within the cortex and across brain regions, is analogous to a band playing music, said George Mashour, a neuroscientist and anesthesiologist at the University of Michigan, Ann Arbor. “You need musical information to come together either in time or space to really make sense,”

“Consciousness and cognitive activity may be similar. If different areas of the brain aren’t in synch or if a critical area that normally integrates cognitive activity isn’t functioning, you could be rendered unconscious.”

, Purdon and colleagues were able to discern a more detailed neural signature of loss of unconsciousness, this time by using EEG alone. Monitoring brain activity in healthy patients for 2 hours as they underwent propofol-induced anesthesia, they observed that as responsiveness fades, high-frequency brain waves (12–35 hertz) rippling across the cortex and the thalamus were replaced by two different brain waves superimposed on top on one another: a low-frequency (<1 hertz) wave and an alpha frequency (8–12 hertz) wave. “These two waves pretty much come at loss of consciousness,”

“We’ve started to teach our anesthesiologists how to read this signature on the EEG”

Anesthesia is not the only state in which consciousness is lost, of course

o measure the gradual breakdown of connectivity between neural networks during natural REM sleep and anesthesia, as well as in brain-injured, unresponsive patients. Using an electromagnetic coil to activate neurons in a small patch of the human cortex, then recording EEG output to track the propagation of those signals to other neuronal groups, the researchers can measure the connectivity between collections of neurons in the cortex and other brain regions.

minimally conscious patients, the magnetically stimulated signals propagated fairly far and wide, occasionally reaching distant cortical areas, much like activations seen in locked-in but conscious patients. In patients in a persistent vegetative state, on the other hand, propagation was severely limited—a breakdown of connectivity similar to that observed in previous tests of anesthetized patients. What’s more, in three vegetative patients that later recovered consciousness, the test picked up signs of increased connectivity before clinical signs of improvement became evident.

“I think understanding consciousness itself is going to help us find successful [measurement] approaches that are universally applicable,” said Pearce.

Since the 1960s, advances in resuscitation had helped to revive thousands of people who might otherwise have died. About 10% or 20% of those people brought with them stories of near-death experiences in which they felt their souls or selves departing from their bodies

According to several international surveys and studies, one in 10 people claims to have had a near-death experience involving cardiac arrest, or a similar experience in circumstances where they may have come close to death. That’s roughly 800 million souls worldwide who may have dipped a toe in the afterlife.

In the 1970s, a small network of cardiologists, psychiatrists, medical sociologists and social psychologists in North America and Europe began investigating whether near-death experiences proved that dying is not the end of being, and that consciousness can exist independently of the brain. The field of near-death studies was born.

in 1975, an American medical student named Raymond Moody published a book called Life After Life.

Meanwhile, new technologies and techniques were helping doctors revive more and more people who, in earlier periods of history, would have almost certainly been permanently deceased.

“We are now at the point where we have both the tools and the means to scientifically answer the age-old question: What happens when we die?” wrote Sam Parnia, an accomplished resuscitation specialist and one of the world’s leading experts on near-death experiences, in 2006. Parnia himself was devising an international study to test whether patients could have conscious awareness even after they were found clinically dead.

Borjigin, together with several colleagues, took the first close look at the record of electrical activity in the brain of Patient One after she was taken off life support. What they discovered – in results reported for the first time last year – was almost entirely unexpected, and has the potential to rewrite our understanding of death.

“I believe what we found is only the tip of a vast iceberg,” Borjigin told me. “What’s still beneath the surface is a full account of how dying actually takes place. Because there’s something happening in there, in the brain, that makes no sense.”

Over the next 30 years, researchers collected thousands of case reports of people who had had near-death experiences

Moody was their most important spokesman; he eventually claimed to have had multiple past lives and built a “psychomanteum” in rural Alabama where people could attempt to summon the spirits of the dead by gazing into a dimly lit mirror.

near-death studies was already splitting into several schools of belief, whose tensions continue to this day. One influential camp was made up of spiritualists, some of them evangelical Christians, who were convinced that near-death experiences were genuine sojourns in the land of the dead and divine

It is no longer unheard of for people to be revived even six hours after being declared clinically dead. In 2011, Japanese doctors reported the case of a young woman who was found in a forest one morning after an overdose stopped her heart the previous night; using advanced technology to circulate blood and oxygen through her body, the doctors were able to revive her more than six hours later, and she was able to walk out of the hospital after three weeks of care

The second, and largest, faction of near-death researchers were the parapsychologists, those interested in phenomena that seemed to undermine the scientific orthodoxy that the mind could not exist independently of the brain. These researchers, who were by and large trained scientists following well established research methods, tended to believe that near-death experiences offered evidence that consciousness could persist after the death of the individua

Their aim was to find ways to test their theories of consciousness empirically, and to turn near-death studies into a legitimate scientific endeavour.

Finally, there emerged the smallest contingent of near-death researchers, who could be labelled the physicalists. These were scientists, many of whom studied the brain, who were committed to a strictly biological account of near-death experiences. Like dreams, the physicalists argued, near-death experiences might reveal psychological truths, but they did so through hallucinatory fictions that emerged from the workings of the body and the brain.

Between 1975, when Moody published Life After Life, and 1984, only 17 articles in the PubMed database of scientific publications mentioned near-death experiences. In the following decade, there were 62. In the most recent 10-year span, there were 221.

Today, there is a widespread sense throughout the community of near-death researchers that we are on the verge of great discoveries

“We really are in a crucial moment where we have to disentangle consciousness from responsiveness, and maybe question every state that we consider unconscious,”

“I think in 50 or 100 years time we will have discovered the entity that is consciousness,” he told me. “It will be taken for granted that it wasn’t produced by the brain, and it doesn’t die when you die.”

it is in large part because of a revolution in our ability to resuscitate people who have suffered cardiac arrest

In his book, Moody distilled the reports of 150 people who had had intense, life-altering experiences in the moments surrounding a cardiac arrest. Although the reports varied, he found that they often shared one or more common features or themes. The narrative arc of the most detailed of those reports – departing the body and travelling through a long tunnel, having an out-of-body experience, encountering spirits and a being of light, one’s whole life flashing before one’s eyes, and returning to the body from some outer limit – became so canonical that the art critic Robert Hughes could refer to it years later as “the familiar kitsch of near-death experience”.

Loss of oxygen to the brain and other organs generally follows within seconds or minutes, although the complete cessation of activity in the heart and brain – which is often called “flatlining” or, in the case of the latter, “brain death” – may not occur for many minutes or even hours.

That began to change in 1960, when the combination of mouth-to-mouth ventilation, chest compressions and external defibrillation known as cardiopulmonary resuscitation, or CPR, was formalised. Shortly thereafter, a massive campaign was launched to educate clinicians and the public on CPR’s basic techniques, and soon people were being revived in previously unthinkable, if still modest, numbers.

scientists learned that, even in its acute final stages, death is not a point, but a process. After cardiac arrest, blood and oxygen stop circulating through the body, cells begin to break down, and normal electrical activity in the brain gets disrupted. But the organs don’t fail irreversibly right away, and the brain doesn’t necessarily cease functioning altogether. There is often still the possibility of a return to life. In some cases, cell death can be stopped or significantly slowed, the heart can be restarted, and brain function can be restored. In other words, the process of death can be reversed.

In a medical setting, “clinical death” is said to occur at the moment the heart stops pumping blood, and the pulse stops. This is widely known as cardiac arrest

In 2019, a British woman named Audrey Schoeman who was caught in a snowstorm spent six hours in cardiac arrest before doctors brought her back to life with no evident brain damage.

That is a key tenet of the parapsychologists’ arguments: if there is consciousness without brain activity, then consciousness must dwell somewhere beyond the brain

Some of the parapsychologists speculate that it is a “non-local” force that pervades the universe, like electromagnetism. This force is received by the brain, but is not generated by it, the way a television receives a broadcast.

In order for this argument to hold, something else has to be true: near-death experiences have to happen during death, after the brain shuts down

To prove this, parapsychologists point to a number of rare but astounding cases known as “veridical” near-death experiences, in which patients seem to report details from the operating room that they might have known only if they had conscious awareness during the time that they were clinically dead.

At the very least, Parnia and his colleagues have written, such phenomena are “inexplicable through current neuroscientific models”. Unfortunately for the parapsychologists, however, none of the reports of post-death awareness holds up to strict scientific scrutiny. “There are many claims of this kind, but in my long decades of research into out-of-body and near-death experiences I never met any convincing evidence that this is true,”

In other cases, there’s not enough evidence to prove that the experiences reported by cardiac arrest survivors happened when their brains were shut down, as opposed to in the period before or after they supposedly “flatlined”. “So far, there is no sufficiently rigorous, convincing empirical evidence that people can observe their surroundings during a near-death experience,”

The parapsychologists tend to push back by arguing that even if each of the cases of veridical near-death experiences leaves room for scientific doubt, surely the accumulation of dozens of these reports must count for something. But that argument can be turned on its head: if there are so many genuine instances of consciousness surviving death, then why should it have so far proven impossible to catch one empirically?

The spiritualists and parapsychologists are right to insist that something deeply weird is happening to people when they die, but they are wrong to assume it is happening in the next life rather than this one. At least, that is the implication of what Jimo Borjigin found when she investigated the case of Patient One.

Given the levels of activity and connectivity in particular regions of her dying brain, Borjigin believes it’s likely that Patient One had a profound near-death experience with many of its major features: out-of-body sensations, visions of light, feelings of joy or serenity, and moral re-evaluations of one’s life. Of course,

“As she died, Patient One’s brain was functioning in a kind of hyperdrive,” Borjigin told me. For about two minutes after her oxygen was cut off, there was an intense synchronisation of her brain waves, a state associated with many cognitive functions, including heightened attention and memory. The synchronisation dampened for about 18 seconds, then intensified again for more than four minutes. It faded for a minute, then came back for a third time.

n those same periods of dying, different parts of Patient One’s brain were suddenly in close communication with each other. The most intense connections started immediately after her oxygen stopped, and lasted for nearly four minutes. There was another burst of connectivity more than five minutes and 20 seconds after she was taken off life support. In particular, areas of her brain associated with processing conscious experience – areas that are active when we move through the waking world, and when we have vivid dreams – were communicating with those involved in memory formation. So were parts of the brain associated with empathy. Even as she slipped irre

something that looked astonishingly like life was taking place over several minutes in Patient One’s brain.

Although a few earlier instances of brain waves had been reported in dying human brains, nothing as detailed and complex as what occurred in Patient One had ever been detected.

In the moments after Patient One was taken off oxygen, there was a surge of activity in her dying brain. Areas that had been nearly silent while she was on life support suddenly thrummed with high-frequency electrical signals called gamma waves. In particular, the parts of the brain that scientists consider a “hot zone” for consciousness became dramatically alive. In one section, the signals remained detectable for more than six minutes. In another, they were 11 to 12 times higher than they had been before Patient One’s ventilator was removed.

“The brain, contrary to everybody’s belief, is actually super active during cardiac arrest,” Borjigin said. Death may be far more alive than we ever thought possible.

“The brain is so resilient, the heart is so resilient, that it takes years of abuse to kill them,” she pointed out. “Why then, without oxygen, can a perfectly healthy person die within 30 minutes, irreversibly?”

Evidence is already emerging that even total brain death may someday be reversible. In 2019, scientists at Yale University harvested the brains of pigs that had been decapitated in a commercial slaughterhouse four hours earlier. Then they perfused the brains for six hours with a special cocktail of drugs and synthetic blood. Astoundingly, some of the cells in the brains began to show metabolic activity again, and some of the synapses even began firing.

At this point the idealist swooshes in: ladies and gentlemen, there is nothing but mind! There is no problem of interaction with matter because matter is mere illusion

idealism has its charms but taking it seriously requires an antipathy to matter bordering on the maniacal. Are we to suppose that material reality is just a dream, a baseless fantasy, and that the Big Bang was nothing but the cosmic spirit having a mental sneezing fit?

pan­psychism: even the lowliest of material things has a streak of sentience running through it, like veins in marble. Not just parcels of organic matter, such as lizards and worms, but also plants and bacteria and water molecules and even electrons. Everything has its primitive feelings and minute allotment of sensation.

The trouble with panpsychism is that there just isn't any evidence of the universal distribution of consciousness in the material world.

it occurred to me that the problem might lie not in nature but in ourselves: we just don't have the faculties of comprehension that would enable us to remove the sense of mystery. Ontologically, matter and consciousness are woven intelligibly together but epistemologically we are precluded from seeing how. I used Noam Chomsky's notion of "mysteries of nature" to describe the situation as I saw it. Soon, I was being labelled (by Owen Flanagan) a "mysterian"

The more we know of the brain, the less it looks like a device for creating consciousness: it's just a big collection of biological cells and a blur of electrical activity - all machine and no ghost.

mystery is quite pervasive, even in the hardest of sciences. Physics is a hotbed of mystery: space, time, matter and motion - none of it is free of mysterious elements. The puzzles of quantum theory are just a symptom of this widespread lack of understanding

The human intellect grasps the natural world obliquely and glancingly, using mathematics to construct abstract representations of concrete phenomena, but what the ultimate nature of things really is remains obscure and hidden. How everything fits together is particularly elusive, perhaps reflecting the disparate cognitive faculties we bring to bear on the world (the senses, introspection, mathematical description). We are far from obtaining a unified theory of all being and there is no guarantee that such a theory is accessible by finite human intelligence.

real naturalism begins with a proper perspective on our specifically human intelligence. Palaeoanthropologists have taught us that the human brain gradually evolved from ancestral brains, particularly in concert with practical toolmaking, centring on the anatomy of the human hand. This history shaped and constrained the form of intelligence now housed in our skulls (as the lifestyle of other species form their set of cognitive skills). What chance is there that an intelligence geared to making stone tools and grounded in the contingent peculiarities of the human hand can aspire to uncover all the mysteries of the universe? Can omniscience spring from an opposable thumb? It seems unlikely, so why presume that the mysteries of consciousness will be revealed to a thumb-shaped brain like ours?

The "mysterianism" I advocate is really nothing more than the acknowledgment that human intelligence is a local, contingent, temporal, practical and expendable feature of life on earth - an incremental adaptation based on earlier forms of intelligence that no one would reg

rd as faintly omniscient. The current state of the philosophy of mind, from my point of view, is just a reflection of one evolutionary time-slice of a particular bipedal species on a particular humid planet at this fleeting moment in cosmic history - as is everything else about the human animal. There is more ignorance in it than knowledge.

related to our ability to have very complex interactions with our environment and with others.

) determining how a semantics based on behavior and goals is capable of explaining the inferential and hierarchical structure of sentences, which is basic for language comprehension;

If one holds the view that phenomenal consciousness does not play any role (that it, as it were, just “sits there” in us) then one commits to a kind of epiphenomenalist view (that consciousness is just a by-product of cognitive processing with no meaningful purpose).

"If the lower animals — which have nervous systems — lack consciousness, the chances that plants without nervous systems have consciousness are effectively nil," Taiz said.

"Being unconscious is in all likelihood an advantage to plants and contributes to their evolutionary fitness," he added.

The project has drawn criticism, mostly because it includes the IIT. Anil Seth, a neuroscientist at the University of Sussex in Brighton, U.K., says the theory is too philosophical—attempting to explain why consciousness exists, rather than how the brain determines whether a stimulus is worthy of conscious attention—to be directly testable.

Despite his misgivings about the project's prospect for a decisive answer, Seth says it will spark discussion and collaboration among scientific rivals. "That itself is to be applauded," he says

Geraint Rees, director of University College London's Institute of Cognitive Neuroscience, complains that reading Tallis is "a bit like trying to nail jelly to the wall." He "rubbishes every current theory of the relationship between mind and brain, whether philosophical or neuroscientific," while offering "little or no alternative,"

cultural memes. The Darwinesque concept originates in Dawkins's 1976 book, The Selfish Gene. Memes are analogous to genes, Dennett has said, "replicating units of culture" that spread from mind to mind like a virus. Religion, chess, songs, clothing, tolerance for free speech—all have been described as memes. Tallis considers it absurd to talk of a noun-phrase like "tolerance for free speech" as a discrete entity. But Dennett argues that Tallis's objections are based on "a simplistic idea of what one might mean by a unit." Memes aren't units? Well, in that spirit, says Dennett, organisms aren't units of biology, nor are species—they're too complex, with too much variation. "He's got to allow theory to talk about entities which are not simple building blocks," Dennett says.

How is it that he perceives the glass of water on the table? How is it that he feels a sense of self over time? How is it that he can remember a patient he saw in 1973, and then cast his mind forward to his impending visit to the zoo? There are serious problems with trying to reduce such things to impulses in the brain, he argues. We can explain "how the light gets in," he says, but not "how the gaze looks out." And isn't it astonishing, he adds, that much neural activity seems to have no link to consciousness? Instead, it's associated with things like controlling automatic movements and regulating blood pressure. Sure, we need the brain for consciousness: "Chop my head off, and my IQ descends." But it's not the whole story. There is more to perceptions, memories, and beliefs than neural impulses can explain. The human sphere encompasses a "community of minds," Tallis has written, "woven out of a trillion cognitive handshakes of shared attention, within which our freedom operates and our narrated lives are led." Those views on perception and memory anchor his attack on "neurobollocks." Because if you can't get the basics right, he says, then it's premature to look to neuroscience for clues to complex things like love.

Yes, many unanswered questions persist. But these are early days, and neuroscience remains immature, says Churchland, a professor emerita of philosophy at University of California at San Diego and author of the subfield-spawning 1986 book Neurophilosophy. In the 19th century, she points out, people thought we'd never understand light. "Well, by gosh," she says, "by the time the 20th century rolls around, it turns out that light is electromagnetic radiation. ... So the fact that at a certain point in time something seems like a smooth-walled mystery that we can't get a grip on, doesn't tell us anything about whether some real smart graduate student is going to sort it out in the next 10 years or not."

Dennett claims he's got much of it sorted out already. He wrote a landmark book on the topic in 1991, Consciousness Explained. (The title "should have landed him in court, charged with breach of the Trade Descriptions Act," writes Tallis.) Dennett uses the vocabulary of computer science to explain how consciousness emerges from the huge volume of things happening in the brain all at once. We're not aware of everything, he tells me, only a "limited window." He describes that stream of consciousness as "the activities of a virtual machine which is running on the parallel hardware of the brain." "You—the fruits of all your experience, not just your genetic background, but everything you've learned and done and all your memories—what ties those all together? What makes a self?" Dennett asks. "The answer is, and has to be, the self is like a software program that organizes the activities of the brain."

Sartre listened to his problem and said simply, ‘You are free, therefore choose — that is to say, invent.’ No signs are vouchsafed in this world, he said. None of the old authorities can relieve you of the burden of freedom. You can weigh up moral or practical considerations as carefully as you like, but ultimately you must take the plunge and do something, and it’s up to you what that something is.

Even if the situation is unbearable — perhaps you are facing execution, or sitting in a Gestapo prison, or about to fall off a cliff — you are still free to decide what to make of it in mind and deed. Starting from where you are now, you choose. And in choosing, you also choose who you will be.

The war had made people realise that they and their fellow humans were capable of departing entirely from civilised norms; no wonder the idea of a fixed human nature seemed questionable.

If this sounds difficult and unnerving, it’s because it is. Sartre does not deny that the need to keep making decisions brings constant anxiety. He heightens this anxiety by pointing out that what you do really matters. You should make your choices as though you were choosing on behalf of the whole of humanity, taking the entire burden of responsibility for how the human race behaves. If you avoid this responsibility by fooling yourself that you are the victim of circumstance or of someone else’s bad advice, you are failing to meet the demands of human life and choosing a fake existence, cut off from your own ‘authenticity’.

Along with the terrifying side of this comes a great promise: Sartre’s existentialism implies that it is possible to be authentic and free, as long as you keep up the effort.

almost all agreed that it was, as an article in Les nouvelles littéraires phrased it, a ‘sickening mixture of philosophic pretentiousness, equivocal dreams, physiological technicalities, morbid tastes and hesitant eroticism … an introspective embryo that one would take distinct pleasure in crushing’.

he offered a philosophy designed for a species that had just scared the hell out of itself, but that finally felt ready to grow up and take responsibility.

In this rebellious world, just as with the Parisian bohemians and Dadaists in earlier generations, everything that was dangerous and provocative was good, and everything that was nice or bourgeois was bad.

Such interweaving of ideas and life had a long pedigree, although the existentialists gave it a new twist. Stoic and Epicurean thinkers in the classical world had practised philosophy as a means of living well, rather than of seeking knowledge or wisdom for their own sake. By reflecting on life’s vagaries in philosophical ways, they believed they could become more resilient, more able to rise above circumstances, and better equipped to manage grief, fear, anger, disappointment or anxiety.

In the tradition they passed on, philosophy is neither a pure intellectual pursuit nor a collection of cheap self-help tricks, but a discipline for flourishing and living a fully human, responsible life.

For Kierkegaard, Descartes had things back to front. In his own view, human existence comes first: it is the starting point for everything we do, not the result of a logical deduction. My existence is active: I live it and choose it, and this precedes any statement I can make about myself.

Studying our own moral genealogy cannot help us to escape or transcend ourselves. But it can enable us to see our illusions more clearly and lead a more vital, assertive existence.

What was needed, he felt, was not high moral or theological ideals, but a deeply critical form of cultural history or ‘genealogy’ that would uncover the reasons why we humans are as we are, and how we came to be that way. For him, all philosophy could even be redefined as a form of psychology, or history.

For those oppressed on grounds of race or class, or for those fighting against colonialism, existentialism offered a change of perspective — literally, as Sartre proposed that all situations be judged according to how they appeared in the eyes of those most oppressed, or those whose suffering was greatest.

She observed that we need not expect moral philosophers to ‘live by’ their ideas in a simplistic way, as if they were following a set of rules. But we can expect them to show how their ideas are lived in. We should be able to look in through the windows of a philosophy, as it were, and see how people occupy it, how they move about and how they conduct themselves.

the existentialists inhabited their historical and personal world, as they inhabited their ideas. This notion of ‘inhabited philosophy’ is one I’ve borrowed from the English philosopher and novelist Iris Murdoch, who wrote the first full-length book on Sartre and was an early adopter of existentialism

What is existentialism anyway?

An existentialist who is also phenomenological provides no easy rules for dealing with this condition, but instead concentrates on describing lived experience as it presents itself. — By describing experience well, he or she hopes to understand this existence and awaken us to ways of living more authentic lives.

Existentialists concern themselves with individual, concrete human existence. — They consider human existence different from the kind of being other things have. Other entities are what they are, but as a human I am whatever I choose to make of myself at every moment. I am free — — and therefore I’m responsible for everything I do, a dizzying fact which causes — an anxiety inseparable from human existence itself.

On the other hand, I am only free within situations, which can include factors in my own biology and psychology as well as physical, historical and social variables of the world into which I have been thrown. — Despite the limitations, I always want more: I am passionately involved in personal projects of all kinds. — Human existence is thus ambiguous: at once boxed in by borders and yet transcendent and exhilarating. —

The first part of this is straightforward: a phenomenologist’s job is to describe. This is the activity that Husserl kept reminding his students to do. It meant stripping away distractions, habits, clichés of thought, presumptions and received ideas, in order to return our attention to what he called the ‘things themselves’. We must fix our beady gaze on them and capture them exactly as they appear, rather than as we think they are supposed to be.

Husserl therefore says that, to phenomenologically describe a cup of coffee, I should set aside both the abstract suppositions and any intrusive emotional associations. Then I can concentrate on the dark, fragrant, rich phenomenon in front of me now. This ‘setting aside’ or ‘bracketing out’ of speculative add-ons Husserl called epoché — a term borrowed from the ancient Sceptics,

The point about rigour is crucial; it brings us back to the first half of the command to describe phenomena. A phenomenologist cannot get away with listening to a piece of music and saying, ‘How lovely!’ He or she must ask: is it plaintive? is it dignified? is it colossal and sublime? The point is to keep coming back to the ‘things themselves’ — phenomena stripped of their conceptual baggage — so as to bail out weak or extraneous material and get to the heart of the experience.

Husserlian ‘bracketing out’ or epoché allows the phenomenologist to temporarily ignore the question ‘But is it real?’, in order to ask how a person experiences his or her world. Phenomenology gives a formal mode of access to human experience. It lets philosophers talk about life more or less as non-philosophers do, while still being able to tell themselves they are being methodical and rigorous.

Besides claiming to transform the way we think about reality, phenomenologists promised to change how we think about ourselves. They believed that we should not try to find out what the human mind is, as if it were some kind of substance. Instead, we should consider what it does, and how it grasps its experiences.

For Brentano, this reaching towards objects is what our minds do all the time. Our thoughts are invariably of or about something, he wrote: in love, something is loved, in hatred, something is hated, in judgement, something is affirmed or denied. Even when I imagine an object that isn’t there, my mental structure is still one of ‘about-ness’ or ‘of-ness’.

Except in deepest sleep, my mind is always engaged in this aboutness: it has ‘intentionality’. Having taken the germ of this from Brentano, Husserl made it central to his whole philosophy.

Husserl saw in the idea of intentionality a way to sidestep two great unsolved puzzles of philosophical history: the question of what objects ‘really’ are, and the question of what the mind ‘really’ is. By doing the epoché and bracketing out all consideration of reality from both topics, one is freed to concentrate on the relationship in the middle. One can apply one’s descriptive energies to the endless dance of intentionality that takes place in our lives: the whirl of our minds as they seize their intended phenomena one after the other and whisk them around the floor,

Understood in this way, the mind hardly is anything at all: it is its aboutness. This makes the human mind (and possibly some animal minds) different from any other naturally occurring entity. Nothing else can be as thoroughly about or of things as the mind is:

Some Eastern meditation techniques aim to still this scurrying creature, but the extreme difficulty of this shows how unnatural it is to be mentally inert. Left to itself, the mind reaches out in all directions as long as it is awake — and even carries on doing it in the dreaming phase of its sleep.

a mind that is experiencing nothing, imagining nothing, or speculating about nothing can hardly be said to be a mind at all.

Three simple ideas — description, phenomenon, intentionality — provided enough inspiration to keep roomfuls of Husserlian assistants busy in Freiburg for decades. With all of human existence awaiting their attention, how could they ever run out of things to do?

For Sartre, this gives the mind an immense freedom. If we are nothing but what we think about, then no predefined ‘inner nature’ can hold us back. We are protean.

way of this interpretation. Real, not real; inside, outside; what difference did it make? Reflecting on this, Husserl began turning his phenomenology into a branch of ‘idealism’ — the philosophical tradition which denied external reality and defined everything as a kind of private hallucination.

For Sartre, if we try to shut ourselves up inside our own minds, ‘in a nice warm room with the shutters closed’, we cease to exist. We have no cosy home: being out on the dusty road is the very definition of what we are.

One might think that, if Heidegger had anything worth saying, he could have communicated it in ordinary language. The fact is that he does not want to be ordinary, and he may not even want to communicate in the usual sense. He wants to make the familiar obscure, and to vex us. George Steiner thought that Heidegger’s purpose was less to be understood than to be experienced through a ‘felt strangeness’.

He takes Dasein in its most ordinary moments, then talks about it in the most innovative way he can. For Heidegger, Dasein’s everyday Being is right here: it is Being-in-the-world, or In-der-Welt-sein. The main feature of Dasein’s everyday Being-in-the-world right here is that it is usually busy doing something.

Thus, for Heidegger, all Being-in-the-world is also a ‘Being-with’ or Mitsein. We cohabit with others in a ‘with-world’, or Mitwelt. The old philosophical problem of how we prove the existence of other minds has now vanished. Dasein swims in the with-world long before it wonders about other minds.

Sometimes the best-educated people were those least inclined to take the Nazis seriously, dismissing them as too absurd to last. Karl Jaspers was one of those who made this mistake, as he later recalled, and Beauvoir observed similar dismissive attitudes among the French students in Berlin.

In any case, most of those who disagreed with Hitler’s ideology soon learned to keep their view to themselves. If a Nazi parade passed on the street, they would either slip out of view or give the obligatory salute like everyone else, telling themselves that the gesture meant nothing if they did not believe in it. As the psychologist Bruno Bettelheim later wrote of this period, few people will risk their life for such a small thing as raising an arm — yet that is how one’s powers of resistance are eroded away, and eventually one’s responsibility and integrity go with them.

for Arendt, if you do not respond adequately when the times demand it, you show a lack of imagination and attention that is as dangerous as deliberately committing an abuse. It amounts to disobeying the one command she had absorbed from Heidegger in those Marburg days: Think!

‘Everything takes place under a kind of anaesthesia. Objectively dreadful events produce a thin, puny emotional response. Murders are committed like schoolboy pranks. Humiliation and moral decay are accepted like minor incidents.’ Haffner thought modernity itself was partly to blame: people had become yoked to their habits and to mass media, forgetting to stop and think, or to disrupt their routines long enough to question what was going on.

Heidegger’s former lover and student Hannah Arendt would argue, in her 1951 study The Origins of Totalitarianism, that totalitarian movements thrived at least partly because of this fragmentation in modern lives, which made people more vulnerable to being swept away by demagogues. Elsewhere, she coined the phrase ‘the banality of evil’ to describe the most extreme failures of personal moral awareness.

His communicative ideal fed into a whole theory of history: he traced all civilisation to an ‘Axial Period’ in the fifth century BC, during which philosophy and culture exploded simultaneously in Europe, the Middle East and Asia, as though a great bubble of minds had erupted from the earth’s surface. ‘True philosophy needs communion to come into existence,’ he wrote, and added, ‘Uncommunicativeness in a philosopher is virtually a criterion of the untruth of his thinking.’

The idea of being called to authenticity became a major theme in later existentialism, the call being interpreted as saying something like ‘Be yourself!’, as opposed to being phony. For Heidegger, the call is more fundamental than that. It is a call to take up a self that you didn’t know you had: to wake up to your Being. Moreover, it is a call to action. It requires you to do something: to take a decision of some sort.

Being and Time contained at least one big idea that should have been of use in resisting totalitarianism. Dasein, Heidegger wrote there, tends to fall under the sway of something called das Man or ‘the they’ — an impersonal entity that robs us of the freedom to think for ourselves. To live authentically requires resisting or outwitting this influence, but this is not easy because das Man is so nebulous. Man in German does not mean ‘man’ as in English (that’s der Mann), but a neutral abstraction, something like ‘one’ in the English phrase ‘one doesn’t do that’,

for Heidegger, das Man is me. It is everywhere and nowhere; it is nothing definite, but each of us is it. As with Being, it is so ubiquitous that it is difficult to see. If I am not careful, however, das Man takes over the important decisions that should be my own. It drains away my responsibility or ‘answerability’. As Arendt might put it, we slip into banality, failing to think.

Jaspers focused on what he called Grenzsituationen — border situations, or limit situations. These are the moments when one finds oneself constrained or boxed in by what is happening, but at the same time pushed by these events towards the limits or outer edge of normal experience. For example, you might have to make a life-or-death choice, or something might remind you suddenly of your mortality,

Jaspers’ interest in border situations probably had much to do with his own early confrontation with mortality. From childhood, he had suffered from a heart condition so severe that he always expected to die at any moment. He also had emphysema, which forced him to speak slowly, taking long pauses to catch his breath. Both illnesses meant that he had to budget his energies with care in order to get his work done without endangering his life.

If I am to resist das Man, I must become answerable to the call of my ‘voice of conscience’. This call does not come from God, as a traditional Christian definition of the voice of conscience might suppose. It comes from a truly existentialist source: my own authentic self. Alas, this voice is one I do not recognise and may not hear, because it is not the voice of my habitual ‘they-self’. It is an alien or uncanny version of my usual voice. I am familiar with my they-self, but not with my unalienated voice — so, in a weird twist, my real voice is the one that sounds strangest to me.

Marcel developed a strongly theological branch of existentialism. His faith distanced him from both Sartre and Heidegger, but he shared a sense of how history makes demands on individuals. In his essay ‘On the Ontological Mystery’, written in 1932 and published in the fateful year of 1933, Marcel wrote of the human tendency to become stuck in habits, received ideas, and a narrow-minded attachment to possessions and familiar scenes. Instead, he urged his readers to develop a capacity for remaining ‘available’ to situations as they arise. Similar ideas of disponibilité or availability had been explored by other writers,

Marcel made it his central existential imperative. He was aware of how rare and difficult it was. Most people fall into what he calls ‘crispation’: a tensed, encrusted shape in life — ‘as though each one of us secreted a kind of shell which gradually hardened and imprisoned him’.

Bettelheim later observed that, under Nazism, only a few people realised at once that life could not continue unaltered: these were the ones who got away quickly. Bettelheim himself was not among them. Caught in Austria when Hitler annexed it, he was sent first to Dachau and then to Buchenwald, but was then released in a mass amnesty to celebrate Hitler’s birthday in 1939 — an extraordinary reprieve, after which he left at once for America.

we are used to reading philosophy as offering a universal message for all times and places — or at least as aiming to do so. But Heidegger disliked the notion of universal truths or universal humanity, which he considered a fantasy. For him, Dasein is not defined by shared faculties of reason and understanding, as the Enlightenment philosophers thought. Still less is it defined by any kind of transcendent eternal soul, as in religious tradition. We do not exist on a higher, eternal plane at all. Dasein’s Being is local: it has a historical situation, and is constituted in time and place.

For Marcel, learning to stay open to reality in this way is the philosopher’s prime job. Everyone can do it, but the philosopher is the one who is called on above all to stay awake, so as to be the first to sound the alarm if something seems wrong.

Second, it also means understanding that we are historical beings, and grasping the demands our particular historical situation is making on us. In what Heidegger calls ‘anticipatory resoluteness’, Dasein discovers ‘that its uttermost possibility lies in giving itself up’. At that moment, through Being-towards-death and resoluteness in facing up to one’s time, one is freed from the they-self and attains one’s true, authentic self.

If we are temporal beings by our very nature, then authentic existence means accepting, first, that we are finite and mortal. We will die: this all-important realisation is what Heidegger calls authentic ‘Being-towards-Death’, and it is fundamental to his philosophy.

Hannah Arendt, instead, left early on: she had the benefit of a powerful warning. Just after the Nazi takeover, in spring 1933, she had been arrested while researching materials on anti-Semitism for the German Zionist Organisation at Berlin’s Prussian State Library. Her apartment was searched; both she and her mother were locked up briefly, then released. They fled, without stopping to arrange travel documents. They crossed to Czechoslovakia (then still safe) by a method that sounds almost too fabulous to be true: a sympathetic German family on the border had a house with its front door in Germany and its back door in Czechoslovakia. The family would invite people for dinner, then let them leave through the back door at night.

As Sartre argued in his 1943 review of The Stranger, basic phenomenological principles show that experience comes to us already charged with significance. A piano sonata is a melancholy evocation of longing. If I watch a soccer match, I see it as a soccer match, not as a meaningless scene in which a number of people run around taking turns to apply their lower limbs to a spherical object. If the latter is what I’m seeing, then I am not watching some more essential, truer version of soccer; I am failing to watch it properly as soccer at all.

Much as they liked Camus personally, neither Sartre nor Beauvoir accepted his vision of absurdity. For them, life is not absurd, even when viewed on a cosmic scale, and nothing can be gained by saying it is. Life for them is full of real meaning, although that meaning emerges differently for each of us.

For Sartre, we show bad faith whenever we portray ourselves as passive creations of our race, class, job, history, nation, family, heredity, childhood influences, events, or even hidden drives in our subconscious which we claim are out of our control. It is not that such factors are unimportant: class and race, in particular, he acknowledged as powerful forces in people’s lives, and Simone de Beauvoir would soon add gender to that list.

Sartre takes his argument to an extreme point by asserting that even war, imprisonment or the prospect of imminent death cannot take away my existential freedom. They form part of my ‘situation’, and this may be an extreme and intolerable situation, but it still provides only a context for whatever I choose to do next. If I am about to die, I can decide how to face that death. Sartre here resurrects the ancient Stoic idea that I may not choose what happens to me, but I can choose what to make of it, spiritually speaking.

But the Stoics cultivated indifference in the face of terrible events, whereas Sartre thought we should remain passionately, even furiously engaged with what happens to us and with what we can achieve. We should not expect freedom to be anything less than fiendishly difficult.

Freedom does not mean entirely unconstrained movement, and it certainly does not mean acting randomly. We often mistake the very things that enable us to be free — context, meaning, facticity, situation, a general direction in our lives — for things that define us and take away our freedom. It is only with all of these that we can be free in a real sense.

Nor did he mean that privileged groups have the right to pontificate to the poor and downtrodden about the need to ‘take responsibility’ for themselves. That would be a grotesque misreading of Sartre’s point, since his sympathy in any encounter always lay with the more oppressed side. But for each of us — for me — to be in good faith means not making excuses for myself.

Camus’ novel gives us a deliberately understated vision of heroism and decisive action compared to those of Sartre and Beauvoir. One can only do so much. It can look like defeatism, but it shows a more realistic perception of what it takes to actually accomplish difficult tasks like liberating one’s country.

Camus just kept returning to his core principle: no torture, no killing — at least not with state approval. Beauvoir and Sartre believed they were taking a more subtle and more realistic view. If asked why a couple of innocuous philosophers had suddenly become so harsh, they would have said it was because the war had changed them in profound ways. It had shown them that one’s duties to humanity could be more complicated than they seemed. ‘The war really divided my life in two,’ Sartre said later.

Poets and artists ‘let things be’, but they also let things come out and show themselves. They help to ease things into ‘unconcealment’ (Unverborgenheit), which is Heidegger’s rendition of the Greek term alētheia, usually translated as ‘truth’. This is a deeper kind of truth than the mere correspondence of a statement to reality, as when we say ‘The cat is on the mat’ and point to a mat with a cat on it. Long before we can do this, both cat and mat must ‘stand forth out of concealedness’. They must un-hide themselves.

Heidegger does not use the word ‘consciousness’ here because — as with his earlier work — he is trying to make us think in a radically different way about ourselves. We are not to think of the mind as an empty cavern, or as a container filled with representations of things. We are not even supposed to think of it as firing off arrows of intentional ‘aboutness’, as in the earlier phenomenology of Brentano. Instead, Heidegger draws us into the depths of his Schwarzwald, and asks us to imagine a gap with sunlight filtering in. We remain in the forest, but we provide a relatively open spot where other beings can bask for a moment. If we did not do this, everything would remain in the thickets, hidden even to itself.

The astronomer Carl Sagan began his 1980 television series Cosmos by saying that human beings, though made of the same stuff as the stars, are conscious and are therefore ‘a way for the cosmos to know itself’. Merleau-Ponty similarly quoted his favourite painter Cézanne as saying, ‘The landscape thinks itself in me, and I am its consciousness.’ This is something like what Heidegger thinks humanity contributes to the earth. We are not made of spiritual nothingness; we are part of Being, but we also bring something unique with us. It is not much: a little open space, perhaps with a path and a bench like the one the young Heidegger used to sit on to do his homework. But through us, the miracle occurs.

Beauty aside, Heidegger’s late writing can also be troubling, with its increasingly mystical notion of what it is to be human. If one speaks of a human being mainly as an open space or a clearing, or a means of ‘letting beings be’ and dwelling poetically on the earth, then one doesn’t seem to be talking about any recognisable person. The old Dasein has become less human than ever. It is now a forestry feature.

Even today, Jaspers, the dedicated communicator, is far less widely read than Heidegger, who has influenced architects, social theorists, critics, psychologists, artists, film-makers, environmental activists, and innumerable students and enthusiasts — including the later deconstructionist and post-structuralist schools, which took their starting point from his late thinking. Having spent the late 1940s as an outsider and then been rehabilitated, Heidegger became the overwhelming presence in university philosophy all over the European continent from then on.

As Levinas reflected on this experience, it helped to lead him to a philosophy that was essentially ethical, rather than ontological like Heidegger’s. He developed his ideas from the work of Jewish theologian Martin Buber, whose I and Thou in 1923 had distinguished between my relationship with an impersonal ‘it’ or ‘them’, and the direct personal encounter I have with a ‘you’. Levinas took it further: when I encounter you, we normally meet face-to-face, and it is through your face that you, as another person, can make ethical demands on me. This is very different from Heidegger’s Mitsein or Being-with, which suggests a group of people standing alongside one another, shoulder to shoulder as if in solidarity — perhaps as a unified nation or Volk.

For Levinas, we literally face each other, one individual at a time, and that relationship becomes one of communication and moral expectation. We do not merge; we respond to one another. Instead of being co-opted into playing some role in my personal drama of authenticity, you look me in the eyes — and you remain Other. You remain you.

This relationship is more fundamental than the self, more fundamental than consciousness, more fundamental even than Being — and it brings an unavoidable ethical obligation. Ever since Husserl, phenomenologists and existentialists had being trying to stretch the definition of existence to incorporate our social lives and relationships. Levinas did more: he turned philosophy around entirely so that these relationships were the foundation of our existence, not an extension of it.

Her last work, The Need for Roots, argues, among other things, that none of us has rights, but each one of us has a near-infinite degree of duty and obligation to the other. Whatever the underlying cause of her death — and anorexia nervosa seems to have been involved — no one could deny that she lived out her philosophy with total commitment. Of all the lives touched on in this book, hers is surely the most profound and challenging application of Iris Murdoch’s notion that a philosophy can be ‘inhabited’.

Other thinkers took radical ethical turns during the war years. The most extreme was Simone Weil, who actually tried to live by the principle of putting other people’s ethical demands first. Having returned to France after her travels through Germany in 1932, she had worked in a factory so as to experience the degrading nature of such work for herself. When France fell in 1940, her family fled to Marseilles (against her protests), and later to the US and to Britain. Even in exile, Weil made extraordinary sacrifices. If there were people in the world who could not sleep in a bed, she would not do so either, so she slept on the floor.

The mystery tradition had roots in Kierkegaard’s ‘leap of faith’. It owed much to the other great nineteenth-century mystic of the impossible, Dostoevsky, and to older theological notions. But it also grew from the protracted trauma that was the first half of the twentieth century. Since 1914, and especially since 1939, people in Europe and elsewhere had come to the realisation that we cannot fully know or trust ourselves; that we have no excuses or explanations for what we do — and yet that we must ground our existence and relationships on something firm, because otherwise we cannot survive.

One striking link between these radical ethical thinkers, all on the fringes of our main story, is that they had religious faith. They also granted a special role to the notion of ‘mystery’ — that which cannot be known, calculated or understood, especially when it concerns our relationships with each other. Heidegger was different from them, since he rejected the religion he grew up with and had no real interest in ethics — probably as a consequence of his having no real interest in the human.

Meanwhile, the Christian existentialist Gabriel Marcel was also still arguing, as he had since the 1930s, that ethics trumps everything else in philosophy and that our duty to each other is so great as to play the role of a transcendent ‘mystery’. He too had been led to this position partly by a wartime experience: during the First World War he had worked for the Red Cross’ Information Service, with the unenviable job of answering relatives’ inquiries about missing soldiers. Whenever news came, he passed it on, and usually it was not good. As Marcel later said, this task permanently inoculated him against warmongering rhetoric of any kind, and it made him aware of the power of what is unknown in our lives.

As the play’s much-quoted and frequently misunderstood final line has it: ‘Hell is other people.’ Sartre later explained that he did not mean to say that other people were hellish in general. He meant that after death we become frozen in their view, unable any longer to fend off their interpretation. In life, we can still do something to manage the impression we make; in death, this freedom goes and we are left entombed in other’s people’s memories and perceptions.

We have to do two near-impossible things at once: understand ourselves as limited by circumstances, and yet continue to pursue our projects as though we are truly in control. In Beauvoir’s view, existentialism is the philosophy that best enables us to do this, because it concerns itself so deeply with both freedom and contingency. It acknowledges the radical and terrifying scope of our freedom in life, but also the concrete influences that other philosophies tend to ignore: history, the body, social relationships and the environment.

The aspects of our existence that limit us, Merleau-Ponty says, are the very same ones that bind us to the world and give us scope for action and perception. They make us what we are. Sartre acknowledged the need for this trade-off, but he found it more painful to accept. Everything in him longed to be free of bonds, of impediments and limitations

Of course we have to learn this skill of interpreting and anticipating the world, and this happens in early childhood, which is why Merleau-Ponty thought child psychology was essential to philosophy. This is an extraordinary insight. Apart from Rousseau, very few philosophers before him had taken childhood seriously; most wrote as though all human experience were that of a fully conscious, rational, verbal adult who has been dropped into this world from the sky — perhaps by a stork.

For Merleau-Ponty, we cannot understand our experience if we don’t think of ourselves in part as overgrown babies. We fall for optical illusions because we once learned to see the world in terms of shapes, objects and things relevant to our own interests. Our first perceptions came to us in tandem with our first active experiments in observing the world and reaching out to explore it, and are still linked with those experiences.

Another factor in all of this, for Merleau-Ponty, is our social existence: we cannot thrive without others, or not for long, and we need this especially in early life. This makes solipsistic speculation about the reality of others ridiculous; we could never engage in such speculation if we hadn’t already been formed by them.

As Descartes could have said (but didn’t), ‘I think, therefore other people exist.’ We grow up with people playing with us, pointing things out, talking, listening, and getting us used to reading emotions and movements; this is how we become capable, reflective, smoothly integrated beings.

In general, Merleau-Ponty thinks human experience only makes sense if we abandon philosophy’s time-honoured habit of starting with a solitary, capsule-like, immobile adult self, isolated from its body and world, which must then be connected up again — adding each element around it as though adding clothing to a doll. Instead, for him, we slide from the womb to the birth canal to an equally close and total immersion in the world. That immersion continues as long as we live, although we may also cultivate the art of partially withdrawing from time to time when we want to think or daydream.

When he looks for his own metaphor to describe how he sees consciousness, he comes up with a beautiful one: consciousness, he suggests, is like a ‘fold’ in the world, as though someone had crumpled a piece of cloth to make a little nest or hollow. It stays for a while, before eventually being unfolded and smoothed away. There is something seductive, even erotic, in this idea of my conscious self as an improvised pouch in the cloth of the world. I still have my privacy — my withdrawing room. But I am part of the world’s fabric, and I remain formed out of it for as long as I am here.

By the time of these works, Merleau-Ponty is taking his desire to describe experience to the outer limits of what language can convey. Just as with the late Husserl or Heidegger, or Sartre in his Flaubert book, we see a philosopher venturing so far from shore that we can barely follow. Emmanuel Levinas would head out to the fringes too, eventually becoming incomprehensible to all but his most patient initiates.

Sartre once remarked — speaking of a disagreement they had about Husserl in 1941 — that ‘we discovered, astounded, that our conflicts had, at times, stemmed from our childhood, or went back to the elementary differences of our two organisms’. Merleau-Ponty also said in an interview that Sartre’s work seemed strange to him, not because of philosophical differences, but because of a certain ‘register of feeling’, especially in Nausea, that he could not share. Their difference was one of temperament and of the whole way the world presented itself to them.

The two also differed in their purpose. When Sartre writes about the body or other aspects of experience, he generally does it in order to make a different point. He expertly evokes the grace of his café waiter, gliding between the tables, bending at an angle just so, steering the drink-laden tray through the air on the tips of his fingers — but he does it all in order to illustrate his ideas about bad faith. When Merleau-Ponty writes about skilled and graceful movement, the movement itself is his point. This is the thing he wants to understand.

We can never move definitively from ignorance to certainty, for the thread of the inquiry will constantly lead us back to ignorance again. This is the most attractive description of philosophy I’ve ever read, and the best argument for why it is worth doing, even (or especially) when it takes us no distance at all from our starting point.

By prioritising perception, the body, social life and childhood development, Merleau-Ponty gathered up philosophy’s far-flung outsider subjects and brought them in to occupy the centre of his thought.

In his inaugural lecture at the Collège de France on 15 January 1953, published as In Praise of Philosophy, he said that philosophers should concern themselves above all with whatever is ambiguous in our experience. At the same time, they should think clearly about these ambiguities, using reason and science. Thus, he said, ‘The philosopher is marked by the distinguishing trait that he possesses inseparably the taste for evidence and the feeling for ambiguity.’ A constant movement is required between these two

As Sartre wrote in response to Hiroshima, humanity had now gained the power to wipe itself out, and must decide every single day that it wanted to live. Camus also wrote that humanity faced the task of choosing between collective suicide and a more intelligent use of its technology — ‘between hell and reason’. After 1945, there seemed little reason to trust in humanity’s ability to choose well.

Merleau-Ponty observed in a lecture of 1951 that, more than any previous century, the twentieth century had reminded people how ‘contingent’ their lives were — how at the mercy of historical events and other changes that they could not control. This feeling went on long after the war ended. After the A-bombs were dropped on Hiroshima and Nagasaki, many feared that a Third World War would not be long in coming, this time between the Soviet Union and the United States.

As a child grows up, the body schema adjusts to the changing body, but its adaptability has limits.

Attention is the selective enhancement of some signals over others, such that the brain’s resources are strategically deployed.

The brain needs to control its attention, just as it controls the body.

In control theory, if a machine is to control something optimally, it needs a working model of whatever it’s controlling. The brain certainly follows this principle in controlling the body.

Just as the body schema is a surreal description of the body, so the attention schema would be a surreal description of attention.

This is called the attention schema theory, a theory that my lab has been developing and testing experimentally for the past five years. It’s a theory of why we insist with such certainty that we have subjective experience. Attention is fundamental.

Perhaps some aspects of consciousness arise from these meta-networks -- and to investigate the proposition, the researchers analysed fMRI scans of 15 people after being injected with psilocybin, the active ingredient in magic mushrooms, and compared them to scans of their brain activity after receiving a placebo.

"One possible by-product of this greater communication across the whole brain is the phenomenon of synaesthesia" -- the experience, common during psychedelic experiences, of sensory mix-up: tasting colours, feeling sounds, seeing smells, and so on.

A truer way of visualising it, he said, would be in three dimensions, with connections between networks forming a sponge-like topography.

"The big question in neuroscience is where consciousness comes from," Petri said. For now, he said, "We don't know."

Broadly speaking, consciousness is often defined as there being an experience of what it’s like to be said creature. (This notion is explored in depth in philosopher Thomas Nagel’s essay, “What is it like to be a bat?”)

Octopuses display signs of curiosity, and Godfrey-Smith believes it’s extremely likely that they’re conscious beings. “I think the exploratory behaviors, the fact that they attend to things, they have good eyes, they evaluate, are little bits of good evidence that there’s something it’s like to be an octopus.”

Based on the current evidence, it seems that consciousness is not particularly unusual at all, but a fairly routine development in nature. “I suspect animal evolution, if were replayed again, it would produce subjectivity of a somewhat similar kind,” he adds. “You can see why it makes biological sense.”

You can’t have a blood family of 300 million, nor even a large enough one to do things like build an agrarian society

In order to have large cities built on agrarianism it was necessary not only to innovate technology, but to transform our very consciousness as it related to how we defined what a person was, both ourselves and others

Instead of needing to have real, flowing blood with common DNA from birth, it was merely necessary to be among the same abstract family organized under a king of some kind — a kind of stand in for the father or patriarch. We developed law and law enforcement as abstract disembodied voices of the father. This allowed total strangers without any family ties to interact in the same society in a constructive and organized way. Thus: civilization as we know it

Those ancient polities have developed finally into the Nation, a kind of tribe so fully abstracted that you can be of any blood and language and religion and still function within it.

So, too, are all other forms of human separation — and the opposition and conflicts they spawn — illusory in nature. We moved beyond blood, but then it was language or religion or fealty that made it impossible to work together, and we warred over that

we’re told these borders mean everything, that they are real and urgent and demand constant sacrifice to maintain.

why is that border there? Why borders?

We’re stuck in a mode of thinking that’s no longer sensible. There isn’t a reason for borders. There never really was, but now more than ever we have no utility for them, no need for them

What humanity has to do is wake up to the reality of post-tribalism. This means seeing through all these invented borders to the truth that we are all people, we are all fundamentally the same, and we can all learn to live with one another.

It was the idea of necessary conflict based on blood that preceded the fights that appeared to justify the belief in that blood-based conflict.

Nations have saturated the entire globe. There are no more frontiers. It’s all Nations butting up against one another.

We are all people of a similar nature and we do have the option to relate to one another as people for the sake of saving our shared homes and futures. We all hunger and thirst and become lonely, we all laugh and weep in the same language. Stripped of confounding symbols we are undivided.

There are a lot of people upset about the illusion of borders. They want a different reality, one in which there are Good Tribes (their tribe) and Bad Tribes (all the other ones).

but the world is already so mixed together they can’t draw those borders anymore. Hence: fascism.

There are no firm foundations for defining this tribe, however, so he’s left to cobble together some kind of ad hoc notion of in- and out-group. Like a magpie he collects ways of dividing people as appeals to his caprice: race, sex, Nation, etc., but there’s no greater sense to it, so it’s all arbitrary, all a mess.

No amount of magical thinking from conservatives can change the reality of globalism, however; what one Nation does to pollute will affect us all, and that is according to the laws of physics. No political movement can change those physics. We have to adapt or perish.

a key part of it is a simple lack of imagination. He just doesn’t realize there’s an option to not have borders, because his entire consciousness is married to the idea of of-me and not-of-me, Us and Them, and if there is no Them there can’t be an Us, and therefore life stops making sense

What has to be true if there are no tribes? We have no need to discriminate among who we may love. Loving and caring for all people as if they were blood family is the path forward

There needs to be a new story for us to share. It’s not enough to stop believing in the old way of borders, we have to actively seek out a new way of thinking and speaking and living that reflects the world as it is and as it can be.

there are others who have more tangible investments in borders: Those who have grown fat off the conflicts driven by these invented borders don’t want us to see how pointless it all is. These billionaires and presidents and kings want us to keep fighting against one another over the borders they so lazily define because it gives them a means of power and control.

We have to be ready for their opposition, however. They’ll do what they can to force us to act as if their borders are real. We don’t need to listen, though we do need to be ready to sacrifice.

Without a globally-coordinated response we can’t resolve a globally-driven problem such as climate change. If we can grant the humanity of all people we can start to imagine ways of relating to one another that aren’t opposed and antagonistic, but which are cooperative and aimed at harmony.

This transformation of consciousness must happen in our own hearts and minds before it can happen in concert.

the Nation has already been shown to be unnecessary because of social globalism. Pick a major city on earth and you’ll find every kind of person living together in peace! Not perfect peace, but not constant and unavoidable war, and that is what counts.

We can’t keep pretending as if borders matter when we can so clearly see that they don’t, but we can’t just have no story at all, there must be a way of contextualizing a future without borders. I don’t know what that story is, exactly, but I believe it is something like love writ large. Once we’re ready to start telling it we can start living it.

What happened to me demands explanation. Modern physics tells us that the universe is a unity—that it is undivided. Though we seem to live in a world of separation and difference, physics tells us that beneath the surface, every object and event in the universe is completely woven up with every other object and event. There is no true separation. Before my experience these ideas were abstractions. Today they are realities. Not only is the universe defined by unity, it is also—I now know—defined by love. The universe as I experienced it in my coma is—I have come to see with both shock and joy—the same one that both Einstein and Jesus were speaking of in their (very) different ways.

Today many believe that the living spiritual truths of religion have lost their power, and that science, not faith, is the road to truth. Before my experience I strongly suspected that this was the case myself. But I now understand that such a view is far too simple. The plain fact is that the materialist picture of the body and brain as the producers, rather than the vehicles, of human consciousness is doomed. In its place a new view of mind and body will emerge, and in fact is emerging already. This view is scientific and spiritual in equal measure and will value what the greatest scientists of history themselves always valued above all: truth.