Consciousness E-Book

John Parrington

• Herausgeber: Icon Books
• Kategorie: Wissenschaft und neue Technologien
• Sprache: Englisch

Seitenzahl: 283

Veröffentlichungsjahr: 2023

Beschreibung

What is the material basis of the thoughts that occur inside our heads? Where do imaginative, creative, or spiritual thoughts come from - can these really be the product of nerve impulses in the brain? And is the human mind radically different from that of other species, or is our uniqueness more superficial than real? In this book, Oxford biologist John Parrington proposes a radical new theory of human consciousness, arguing that a qualitative leap in consciousness occurred during human evolution as language and tool use transformed our brains. Rejecting outdated views of the brain as a hard-wired circuit diagram, he draws on the latest insights from neuroscience to show that meaning is created within our heads through a dynamic interaction of oscillating brain waves. This new model of consciousness not only provides a material basis of our innermost thoughts but also explains why the mind can sometimes go wrong, causing deep mental distress.

Leseprobe

Hot Science is a series exploring the cutting edge of science and technology. With topics from big data to rewilding, dark matter to gene editing, these are books for popular science readers who like to go that little bit deeper …

AVAILABLE NOW AND COMING SOON:

Destination Mars:

The Story of Our Quest to Conquer the Red Planet

Big Data:

How the Information Revolution is Transforming Our Lives

Gravitational Waves:

How Einstein’s Spacetime Ripples Reveal the Secrets of the Universe

The Graphene Revolution:

The Weird Science of the Ultrathin

CERN and the Higgs Boson:

The Global Quest for the Building Blocks of Reality

Cosmic Impact:

Understanding the Threat to Earth from Asteroids and Comets

Artificial Intelligence:

Modern Magic or Dangerous Future?

Astrobiology:

The Search for Life Elsewhere in the Universe

Dark Matter & Dark Energy:

The Hidden 95% of the Universe

Outbreaks & Epidemics:

Battling Infection From Measles to Coronavirus

Rewilding:

The Radical New Science of Ecological Recovery

Hacking the Code of Life:

How Gene Editing Will Rewrite Our Futures

Origins of the Universe:

The Cosmic Microwave Background and the Search for Quantum Gravity

Behavioural Economics:

Psychology, Neuroscience, and the Human Side of Economics

Quantum Computing:

The Transformative Technology of the Qubit Revolution

The Space Business:

From Hotels in Orbit to Mining the Moon – How Private Enterprise is Transforming Space

Game Theory:

Understanding the Mathematics of Life

Hothouse Earth:

An Inhabitant’s Guide

Nuclear Fusion:

The Race to Build a Mini-Sun on Earth

The Science of Music:

How Technology has Shaped the Evolution of an Artform

Biomimetics:

How Lessons from Nature can Transform Technology

Hot Science series editor: Brian Clegg

Published in the UK and USA in 2024 byIcon Books Ltd, Omnibus Business Centre,39–41 North Road, London N7 9DPemail: [e-mail]

ISBN: 978-183773-078-0eBook: 978-183773-079-7

Text copyright © 2023 Icon Books

The author has asserted their moral rights.

No part of this book may be reproduced in any form, or by any means, without prior permission in writing from the publisher.

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Printed and bound in the UK.

ABOUT THE AUTHOR

John Parrington is an Associate Professor in Molecular and Cellular Pharmacology and a Tutorial Fellow in Medicine at the University of Oxford. He is the author of three previous books and over 110 peer-reviewed articles. His research focuses on how chemical signals regulate important processes in the body.

CONTENTS

1 What is Consciousness?

2 Tools and Symbols

3 Nerves and Brains

4 Evolving Minds

5 Thought and Reason

6 The Sensual World

7 Learning and Memory

8 Mind Chemistry

9 Philosophy of Mind

10 Individual and Society

11 Information and Meaning

12 Chance and Design

13 Structure and Function

14 Circuits and Waves

15 Free Will and Selfhood

16 Consciousness and the Unconscious

17 Modernity and its Contradictions

18 Sanity and Madness

19 How Ideas Change

20 Future of Mind

References

WHAT IS CONSCIOUSNESS? 1

What is the material basis of the thoughts that occur inside our heads? What makes my thoughts different from yours and why do different people have distinctive personalities? Where do imaginative, creative or spiritual thoughts come from – can these really simply be the product of nerve impulses in the brain? Is human consciousness so different from that of other species or is our uniqueness more superficial than we might imagine?

These are fundamental questions – some would say among the biggest unresolved questions in science. Indeed, such is their nature that some influential philosophers doubt whether science is even capable of answering them. Because of this, it may seem presumptuous to even try and begin to provide answers to such questions in a single book, but that is what I’m aiming to do here. In so doing, I’ll be drawing not only on the latest evidence from neuroscience and psychology, but also on a range of philosophical insights.

Certainly, questions like the ones above have taxed the minds of philosophers for millennia and have probably been a source of debate long before human beings first discovered ways to record our thoughts and ideas. In recorded history, one of the first people to speculate about the nature of consciousness was the philosopher Aristotle.

He believed that consciousness exists as a continuum of different types of ‘souls’1: thus plants have a vegetative or nutritive soul, which controls their growth, nutrition and reproduction; animals have such characteristics too, but also a sensitive soul, which allows them to perceive things and move about, and they also have fears and desires; and finally humans have all of these characteristics, but also a rational soul that allows them to reason and reflect. It was an interesting viewpoint that could have been explored further scientifically, but for the next 2,000 years, such was the stifling power of religion that there were many barriers to developing a scientific understanding of consciousness.

Figure 1. Aristotle’s three types of soul.

Dualistic view

But things particularly began to change about 400 years ago. Inspired by William Harvey’s demonstration that the heart functions like a pump, the philosopher René Descartes, one of the foremost thinkers in the world in the first half of the 17th century, proposed that the body could be seen as acting like a machine. Descartes also saw our ability to view ourselves and the world around us in a rational way as proof that consciousness was real – the basis of his famous statement ‘I think, therefore I am’ – and he even suggested that some aspects of human behaviour, such as unconscious reflexes, could be explained by material forces.2 Yet he argued that the ‘soul’ would always remain unknowable to science. Descartes’ caution on this matter may have been influenced by his religious views, and also by how little was known about the mechanistic basis of consciousness at this time. However, this ‘Cartesian dualism’ relating to differences between body and mind has been a problematic feature of discussions about consciousness ever since.3

In the late 17th and early 18th centuries, other philosophers became more willing to subject consciousness in all its aspects to scientific enquiry. John Locke and then David Hume argued that the mind could be viewed as a ‘blank slate’ and each individual human consciousness therefore was just the accumulation of experiences acquired since birth.

Although a properly materialist view of consciousness – meaning an explanation of the human mind without recourse to supernatural causes – a problem with this understanding was that it did not explain how each individual mind feels like a unified, individual phenomenon, rather than just a mass of unconnected experiences.4 In fact, we will see later that this ‘binding problem’ has become a major issue of debate and study in modern neuroscience. Another problem with Locke and Hume’s view of the mind is that by ignoring the role of differences in individual biology in the formation of consciousness, they did not explain why two different people growing up in a very similar environment can turn out radically different in their abilities, personality, temperament and so on. This viewpoint also failed to explain why human consciousness seems so different from that of animals.

One philosopher of this period who did engage with the question of how human consciousness might be related to our biology was Gottfried Wilhelm Leibniz.5 He suggested that the inner workings of the mind might be likened to the different pieces of machinery in a textile mill – a striking new phenomenon in the 18th century. Yet he claimed that even if one could explore in detail the insides of such a mind, while this could reveal its components, it was unlikely to take us any closer to understanding the human mind, partly because of the deeply subjective nature of each individual human consciousness, but also because of the complexity of the interactions between the mind’s individual parts.

Hard problem

Leibniz’s scepticism about the possibility of a truly materialist explanation of consciousness might be seen as justified given how little was known about the brain at that time. Yet while scientific knowledge about this organ has advanced dramatically, it is not clear that we are any closer to a proper understanding of consciousness. The philosopher David Chalmers has expressed this conundrum by what he calls the ‘hard problem of consciousness’.6 Chalmers believes that neuroscience may soon allow us to understand how we learn, store memories, perceive things, react instantly to a painful stimulus or hear our name spoken across a room at a noisy party. Indeed, he thinks these may be relatively easy aspects of consciousness to decipher, at least with sufficient research time and money.

In contrast, Chalmers sees the ‘hard problem’ of consciousness as explaining that subjective sense we have as individuals of being us, with all that implies in terms of our specific responses to, say, a sunset or a work of art, the particular way we felt when we first fell in love or any personal experience, in purely material terms. It is the difficulty in explaining such subjectivity that has led some to view the problem of explaining consciousness in this way as ultimately impossible. However, surely this viewpoint does not take us much further than we got with Descartes, at least if our aim is a materialistic view of consciousness. Indeed, some critics have accused Chalmers and other proponents of the ‘hard problem’ of clinging to the idea of a ‘soul’ that is forever unknowable to scientific methods, just like that of Descartes.7 My personal feeling is that Chalmers has identified a real problem for explanations of consciousness that seek to describe it in purely material terms, yet I do not believe it is an insurmountable problem for science, for reasons I will outline later.

The debate about whether we will ever understand the material nature of consciousness is not just one between philosophers on one side and neuroscientists on the other. Daniel Dennett is a philosopher, but one who has also championed a very materialist view of consciousness. Dennett is a critic of idealist models of human consciousness, meaning ones not based on the material properties of our brains.8 Such models ultimately rely on there being some kind of homunculus – meaning ‘little human’ – directing things from inside the brain, but this only begs the question of who controls the brain of the homunculus and so on. Instead, Dennett proposes a ‘bottom-up’ approach, which sees the mind as the combined product of unconscious, evolved processes that somehow combine to provide the appearance of an individual ‘I’, yet in reality has no conscious entity at its core or, for that matter, a specific place in the brain where ‘it all comes together’.

Figure 2. Cartesian dualism and the idea of a homunculus controlling the brain.

Dennett has also criticised theories of consciousness that rely on what he calls ‘skyhooks’ – explanations of complexity that do not build on lower, simpler layers. Yet ironically, in his own view of consciousness, Dennett has used what I consider a skyhook: memes.9 Nowadays, a meme tends to signify those images or video clips – often humorous, cringeworthy or carrying some life message – that can spread so rapidly on social media. The term was first used in 1976 by Richard Dawkins, in his book The Selfish Gene, to describe an idea, behaviour or style that spreads between people – examples being ‘tunes, ideas, catch-phrases, clothes fashions, ways of making pots or of building arches’. Dawkins argued that ‘just as genes propagate themselves in the gene pool by leaping from body to body via sperm or eggs, so memes propagate themselves in the meme pool by leaping from brain to brain via a process which, in the broad sense, can be called imitation’.10

As a description of how popular images can spread rapidly across the internet, almost like a viral infection, this was a remarkably prophetic and insightful vision. However, using memes as an example of how human consciousness works seems to me to be an idealist viewpoint because it suggests that ideas are independent entities with a separate identity from the minds they inhabit, when what we really need to do to establish a materialist theory of consciousness is to show how ideas originate organically within individual human brains, as well as passing between them.

Here, Chalmers’ point about there being a ‘hard’ problem within consciousness also seems relevant. For another criticism that could be made of Dennett’s view is that, even if his ‘bottom-up’ approach that sees consciousness as something emerging from a mass of unconscious neural impulses is true, that still leaves the problem of explaining the very subjective nature of an individual human consciousness in material terms. Even if we also accept the idea that consciousness is the product of many unconscious processes distributed across the brain, that still leaves the question of why it is that as human individuals we have that very clear and vivid sense of ourselves as individual entities.

One area of potential confusion when discussing consciousness is what we mean by this term. We saw how Aristotle believed there were three types of consciousness, with only humans possessing the rational, ‘higher’ form. The idea that humans are unique compared to other species continued with the Judeo-Christian philosophical tradition. Yet the past half millennium has seen an erosion of the idea that there is anything unique about human beings and our place in the universe. This trend began with Nicolaus Copernicus’ demonstration in 1543 that, instead of being at the centre of the universe, the Earth is merely a satellite of the Sun, which we now know to be just one star among many others.

Mental spectrum

A further blow to our egos came with Charles Darwin and Alfred Russel Wallace’s theory of evolution by natural selection, most famously expounded in Darwin’s The Origin of Species, published in 1859, which showed that humans are only one of many branches on the tree of evolutionary change.11 We now appreciate that while life itself has existed on Earth for 4 billion years, humans only diverged from our closest relative, the chimpanzee, between 6 to 10 million years ago. Moreover, comparisons of the human and chimp genome show these are 96 per cent similar in DNA sequence. Because of this genetic continuity between humans and other species, some philosophers and neuroscientists have begun to look for such continuity in consciousness. For instance, neuroscientist Christof Koch has recently claimed that ‘consciousness is … probably present in most of metazoa, most animals, [and] it may even be present in very simple systems like a bacterium’.12

The idea that consciousness is something shared by many species underlies a now famous article by the philosopher Thomas Nagel in which he asked: ‘What is it like to be a bat?’13 In this, Nagel makes two major assumptions. One is that ‘conscious experience is a widespread phenomenon’ present in many animals, particularly mammals. Another is that such an experience has a ‘subjective’ character. Following this, Nagel argues that since bats have a different sensory apparatus to humans, relying on sonar to navigate the world far more than by a visual system like most people, it would be very difficult to imagine what it would be like to be a bat. Nagel uses this fact to question whether scientific methods can ever reveal the true nature of consciousness in a materialist, objective fashion, or whether this will always be outside science’s reach. His argument is similar to Chalmers’ notion of a ‘hard problem’ in consciousness, but with added emphasis, since imagining what it feels like to be a bat is surely even more difficult than imagining being another human.

However, what if Nagel’s assumptions are incorrect? What if the self-conscious awareness that we humans generally mean when we talk about having a consciousness is not shared with other species? What if, as a consequence, there is also no sense that any other species can have a subjective sense of themselves as an individual, but rather they are a complex mass of feelings and sensations but with nothing like the individual identity we take for granted as individual humans? So while other species may be conscious in one sense, this is very different from our human self-conscious awareness. This may seem a bold claim, but it explains one major difference between humans and other species – our capacity for transforming the world around us with each new generation; it is this that in 40,000 years has allowed us to go from scratching a living from the Earth to sending rockets to Mars.

In contrast, no other species on the planet, including our closest biological cousins, the great apes, has shown any capacity to transform the world around them in the way that human beings do. Not that this capacity is always a good thing, as witnessed by the fact that human civilisation may be heading for catastrophe in the form of global warming, chemical pollution, mass extinction of other species or the threat of a nuclear holocaust, but it is a unique capacity nevertheless, and I would argue that it is a direct manifestation of something else distinctive about human beings, namely our powers of conceptual thought and language, coupled with our ability to design, and redesign, new types of tools and technologies. So let us now look at how these capacities arose during our evolution from apes and how this led to human consciousness becoming a very specific entity on Earth.

TOOLS AND SYMBOLS 2

An idea I will keep returning to in this book is that human self-conscious awareness arose as a consequence of two other unique human attributes – our capacity for language and our ability to continually transform the world around us by designing and using tools. However, there is also another vital factor in what makes humans unique, which is our brains: these are not just much bigger than those of other primates, but radically different in structure and function. I see these three capacities as interconnected in terms of their evolution.

Is it really true that human language and the way we use technologies to transform the world around us are unique to our species? Some would dispute this uniqueness. For instance, they might point to the fact that other species communicate through various sounds and gestures or to evidence that other primates and even some other types of animal, such as crows, develop and use tools. I believe that such arguments miss the key qualitative difference between human beings and other species. To understand why, it is worth looking in more detail at how humans first evolved from apes.

Surprisingly, the first person to identify the correct sequence of human evolution was not Charles Darwin, as one might expect, but Friedrich Engels.1 Despite being known primarily as a political activist and thinker, Engels also had a profound interest in natural science, and in an essay he wrote in 1876, he proposed that humans first began to diverge significantly from other primates when our ancestors started walking on two legs. This freed the hands for using and designing tools, and as a consequence, proto-humans began using tools in a systematic way to transform the world around them. Importantly, such design and subsequent use of different types of tools was carried out with other proto-humans in a socially cooperative manner. Because of the need to communicate with their neighbours about how to carry out such innovative actions, our ancestors also began to develop the first forms of language. Subsequently, the development of both systematic tool design and use, and language, led to a dramatic growth and restructuring of the brain.

Engels’ proposed sequence of events differed from that of Darwin, who argued that the development of a large brain preceded bipedalism, tool use and language.2 However, subsequent accumulated fossil and DNA evidence have confirmed that what Engels proposed is correct, although, in contrast to the linear progression that he envisaged, human evolution has been more a case of multiple proto-humans with different characteristic features co-existing and with many blind alleys ending in extinction along the path to Homo sapiens.3

If some other species use tools, what is distinctive about human tool use? A key difference is that tool use by other species tends to be both occasional and also very limited in the type of tools that are created. In contrast, a unique feature of our species is that practically all of our interactions with the world are through tools that we have created.

Figure 3. Evolution of humans from apes.

As well as the fact that tool use is systematic to the way that humans interact with the world, in contrast to the more accidental and occasional use of tools by some other species, another key feature of human beings is the way we are continually in a process of inventing new types of tools and technologies. While this was a relatively slow business early in our prehistory, in modern times, it has accelerated to the point that we now take for granted the way that novel technologies rapidly develop during the lives of each new generation.

Indeed, such is the speed of change nowadays that a characteristic feature of modern life is keeping up with the latest technological developments. I doubt I am the only middle-aged individual who struggles to understand how many of the ‘apps’ on my mobile phone work, in contrast to my children who rapidly moved from computer keyboard to tablet to phone screen and who seize the opportunities offered by the latest forms of social media, while laughing at their father’s continuing use of ones they see as totally outdated.

Symbolic species

If these are some unique aspects of human tool design and use, what about language? Here, one mistake to make would be to assume that human language is just a means of communication, and because other species communicate with each other, there is nothing unique about this human ability. However, this overlooks a highly distinctive feature of human language, which is that it is an interconnected system of abstract symbols, linked together by grammar in such a way that it can convey complex meaning. It is for this reason that only human beings are able to use language to convey complex ideas like past, present and future, individual versus society, location in space and even more abstract concepts.

Showing how this capacity is a unique feature of human biology, intensive attempts to teach sign language to our closest primate cousins, chimpanzees and gorillas, in the 1970s, demonstrated that, while such species can learn to associate words with objects and even emotions, these other primates lack our grammatical capacity and as a consequence the ability of human beings to represent the world conceptually through abstract symbols.4 This is a key difference between humans and apes that I will explore in more detail later.

Underpinning the unique human attributes of systematic tool use and language is a brain that has evolved to give us the capacity to handle these attributes in a meaningful way. Indeed, we will see later that there is a good reason for this, for both our use of tools to transform the world around us, and our use of language to communicate with each other, have, during our evolution and also in the development of each individual human being, led to the transformation of the human brain in a highly distinctive way. A useful analogy here is to see tool use and language as activities that do not just guide our interactions with the external world, but also act as ‘mental tools’ that have transformed the brain in the process.

If systematic use and development of technology and language capacity are unique features of our species, what about the way our brain works compared to other species? Here we face a problem for while it is possible to objectively study tool use and language in humans and compare this to the abilities of other animals, what goes on inside an individual brain of a human or other species, particularly at the subjective level, is far harder to assess.

Yet I believe we can gain an objective and scientific understanding of what makes human consciousness unique, both through psychological analysis and by studying the ways in which the human brain differs from those of other species in both structure and function. I will also be exploring what we have learned so far in this quest later in this book. However, what we also need is a firm conceptual foundation for such analysis and in particular one that requires a better understanding of the links between human thought and language, and how language has transformed human thought in a way that makes it qualitatively different from the thoughts of other species. These are topics that I will look at in this and later chapters.

For some, the idea of using scientific methods to understand the basis of an individual person’s thought processes can seem like an impossible task. This surely is at the heart of David Chalmers’ ‘hard problem of consciousness’, meaning the difficulty of explaining human consciousness in objective, scientific terms because of the impossibility of ‘getting inside’ the head of another person and observing their thoughts. In fact, we even face a problem in trying to get inside our own heads, since the moment we try to explain our innermost thoughts, we are potentially altering them in that process of explanation.

Inner speech

One of the early pioneers of psychology, William James, likened the problem of attempting to observe our own thoughts to ‘trying to turn up the gas quickly enough to see how the darkness looks’.5 Yet I believe we can gain important insights into both our own and other people’s thought processes because of what I have said previously about two unique aspects of human beings compared to other species, these being our ability to design and use tools and our capacity for language. I would also argue that our language capacity in particular shapes our thought processes in ways that we can begin to study and understand.

Someone who played a pioneering role in this respect was the psychologist Lev Vygotsky. He argued that ‘egocentric speech’ – children’s tendency to talk to themselves as they play – is the first stage in a child starting to organise their actions using words and that while this form of speech seems to disappear, what is actually happening is it becomes internalised as ‘inner speech’, which in adults plays a central role in the organisation and development of our thoughts.6 So by studying egocentric speech it should be possible to gain insights into the particular character of inner speech. It is also possible to understand inner speech better by studying outer speech and then extrapolating to the likely character of the inner speech from which the outer version originates in the brain. Finally, we can introspectively analyse our own inner speech and thereby try and learn about its character.

Such studies combined suggest that inner speech differs from outer speech in some important ways.7 It is likely to be much more rapid, and far more fluid in meaning, than the speech we use in conversation with others. There are also probably different types of inner speech, ranging from that which emerges from our innermost, half-formed thoughts to the type that structures our outer speech when we express ourselves to others.

An important consequence of human inner consciousness being structured by language is that this gives a particular social dimension to human consciousness that is lacking in other species. Originating as they do in society, words necessarily infuse our thoughts with social meaning. Given that our inner speech is not merely a reflection of our present circumstances, but also carries with it the memory of past ones, this means that our inner consciousness must be deeply infused with past social interactions that we have had with other people, for instance, parents, siblings, teachers, friends and colleagues.8

While language is the primary structurer of inner human consciousness, we should not forget what I have said about tools also being central to what it means to be human. For a distinctive feature of human beings is not only that we interact with the world around us through tools, but that these continually change with each new generation. This is likely to significantly affect not just humanity as a whole but each individual consciousness.

Cultural tools

One has only to think of the impact that the invention of reading and writing must have had on human thought processes, or more recently the ways we have begun to communicate using the internet, to see how profoundly such changes may affect the workings of the inner human psyche. Particularly relevant to the ways that social media may now be affecting individual human consciousnesses is that this is not only based around the written word, but also visual images, videos, music, abstract symbols and so on. In fact, not only spoken language but a variety of what we might call ‘cultural tools’, which can include music, visual art, literature and mathematical and scientific symbols, are all distinctive to humanity and could each have an influence on human consciousness.9

Figure 4. Vygotsky’s theory of cognitive development.

If language and also other cultural tools are central to structuring our inner consciousness, where does this leave thought? Here it is worth returning to what I said previously about the similarities and differences between humans and other species. Given that human brains have much in common with those of other mammals, particularly other primates, not just at basic molecular and cellular levels but also in terms of different brain regions and their interconnections, it seems likely that at the most basic level of thought processes we also share much in common. Yet the lack of language and other cultural tools in other species surely must have a profound impact on their inner consciousness.

I said previously that a key feature of language that distinguishes it from animal communication is that it is an interconnected system of abstract symbols linked by grammar. However, since only we have such a system, surely this means that the inner consciousness of other species cannot have that language-based, conceptual underpinning that we take for granted. In fact, later in this book I will be looking at the question of whether non-language-based types of conceptual thought might exist in other species, particularly non-human primates. None of this is to say that other species cannot have very sophisticated behaviours, feelings and social interactions, but this surely raises the question of whether any other species has a unified sense of self and their place in the world as we do.

To return to something I mentioned previously, Thomas Nagel’s essay ‘What is it like to be a bat?’, although Nagel intended this question to reveal the limits to how much we can ever know scientifically about the subjective character of consciousness, for me this question is itself problematic. This is because not only could we never know what it feels like to be a bat, maybe neither could a bat, at least not in terms of being able to express or be self-consciously aware of such a feeling. The key then to understanding human consciousness is language and tool-use, but that still leaves the question of how that consciousness manifests itself in terms of molecular and cellular signals in the brain, activities in different brain regions and interconnections between those regions, which are issues I will now begin to explore in more detail by looking at nerves and brains.

NERVES AND BRAINS 3

If we want to understand how human consciousness emerges from a material object, the brain, ultimately we need to know more about how the brain functions as one of the body’s organs. Here though we face a problem. For although our understanding of how other organs function is now fairly clear, this is still far from the case when it comes to the brain. I mentioned previously how William Harvey transformed our view of how the human body works when he demonstrated that the heart can be thought of as a pump.1 We also now understand how the liver stores and creates energy and destroys toxins, the kidney flushes out waste products from the blood and maintains its concentration of salts and other substances vital for life, and the stomach and intestines digest and absorb food.

Of course, every year we gain important new insights into how our organs work.2 A strength of science is its ability to cast new light on processes thought to be already fully understood. Yet, in general, our understanding of how most human organs function is well advanced. In contrast, although our understanding of the fine detail of the molecular and cellular processes that occur in the brain have increased dramatically over recent decades, I believe that even most neuroscientists would agree that things are very different when it comes to understanding how the brain’s components work together as a unified whole.

In order to advance our own understanding of brain function and how this relates to human consciousness, it would be useful to begin by defining the brain’s basic components. The base unit of the brain is the nerve cell, or neuron.3