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Introduction | Return of Consciousness
Chapter 1 | What is consciousness?
Chapter 2 | Who is conscious?
Chapter 3 | Animal Consciousness
Chapter 4 | Consciousness and the Rest
Chapter 5 | Consciousness and the Brain
Chapter 6 | Following the Footsteps of Consciousness
Chapter 7 | Why We Need a Theory of Consciousness
Chapter 8 | About the Complete
Chapter 9 | Tools for Measuring Consciousness
Chapter 10 | Transcendental Mind and Pure Consciousness
Chapter 11 | Does consciousness have a function?
Chapter 12 | Consciousness and Computationalism
Chapter 13 | Why Computers Can't Have Experience
Chapter 14 | Is Consciousness Everywhere?
Conclusion | Why This Matters

Acknowledgements
annotation
References
Translator's Note
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A book that boldly expands the horizons of science!
The most influential theory in the current 'theory of consciousness',
Speaking of Integrated Information Theory (IIT)

“Christoph Koch, who has presented some of the most controversial hypotheses about the origins of consciousness, addresses the question of consciousness more deeply than his previous works.
In this book, readers can comprehensively view the various theories of consciousness that have emerged in the world over the past 20 years and read his own interpretation.
Above all, the virtue of this book is that it most persuasively describes what the 'integrated information theory' he proposed is.” ― Jaeseung Jeong

The two most prominent hypotheses explaining consciousness in neuroscience today are:
Integrated Information Theory (IIT), which is based on panpsychism but embraces and quantifies it to overcome its limitations, and Global Neuronal Workspace Theory (GNWT), which attempts a functionalist explanation of consciousness based on a computational perspective.

Koch criticizes GNWT for its complete lack of interest in the 'causal powers [properties]' of the fundamental system (within living organisms), and for pointing out that 'purely computational explanations' have fatal limitations.
Furthermore, empirical studies have shown that the brain region involved in conscious states is the 'posterior cortical hot zone' claimed by IIT, not the 'prefrontal cortex' claimed by GNWT.
The author cites numerous cases in the book where people retain conscious experience even when the prefrontal cortex is damaged or even removed.


Thus, Koch argues that IIT is currently the most influential and persuasive theory in the theory of consciousness.
Research supporting the author's claims is also in full swing.
Since 2019, cognitive neuroscience researchers have been conducting pioneering experiments to validate these two leading theories of consciousness, exploring what they call an "antagonistic cooperative relationship" to determine which theory holds the most promise for uncovering the mechanisms of consciousness.

This study (Testing Hypotheses by Adversarial Collaboration) mainly tests the following three hypotheses.
① Which brain regions are involved in the state of consciousness? ② How is conscious perception maintained? ③ What is the connectivity between cortical regions during perception?
The predictions for ① and ② are leaning towards IIT dominance, and the prediction for ③ is inconclusive.


As such, the current neuroscience community and the two major scientific journals, Nature and Science, accept IIT as a 'verified' theory as a strong theory of consciousness, but it is also controversial as it is a very innovative theory that influences the ethical judgments of individuals and society.
But the emergence of a new paradigm always begins with discussions that seem impossible to imagine.


In The Sense of Life Itself, Koch defends and strengthens this theory, taking numerous critical perspectives into account, and develops a 'very sophisticated theoretical account' of consciousness.
Additionally, the philosophical approach, which refers to the 20-year intellectual landscape in the neurobiology of consciousness, also serves as a major axis of this discussion.
As the translator points out, in a word, this book is “a philosophical and scientific book on the theory of consciousness.”


In this book, Koch integrates and condenses the various components of the theoretical explanations presented in his previous works on consciousness, 『Consciousness』 and 『Explorations of Consciousness』, and presents a fundamental theory of the 'nature of consciousness'.
As Professor Jeong Jae-seung notes, the virtue of this book is that it delves deeper into the question of consciousness than previous works, and that it “provides the most persuasive account of what integrated information theory is.”


Consciousness is about 'being'
The challenge of defining consciousness as 'experience'!

- What evokes the 'experience' of life?
- Does artificial intelligence imply artificial 'consciousness'?

“The Sense of Life Itself” is a book that answers the question, “What is consciousness?” with “The Sense of Life Itself.”
In other words, we see consciousness as the totality of our experiences [feelings] and the totality of our senses in life.
This process of consciousness is explained neuroscientifically, and the relationship between experience and cerebral cortex activity (activation) is experimentally proven, and the 'integrated information theory' is presented as the key to solving the mystery of consciousness.
It shares the broad framework of the problem presented by panpsychism, but goes beyond the limitations of panpsychism and shows that the neural mechanism of consciousness is ‘quantitative’, ‘consistent’, and ‘provable’ through experiments.

How does the brain generate subjective "experience"? What are the undeniable properties (axioms, postulates) of "experience"? Koch states, "Every feeling I use is an experience," and, contrary to the conventional wisdom that regards experience as a higher-order category than feeling, defines experience and feeling as equivalent.
In other words, we focus on ‘experience’ and conduct and analyze various thought experiments and research.
He argues for the validity of 'integrated information theory', a quantitative theory that starts from 'experience' and moves to 'brain', by mentioning perception-response tests, optical illusion and illusion experiments, zombie actors, split-brain and brain-wiring experiments, the case of Terry Schiavo, who was in a vegetative state for 15 years, examples of people with consciousness disorders or living without parts of the brain, the Leibniz Mill thought experiment, and in silico evolutionary games.


This view of Koch's is very challenging, and it is also a special and solid foundation for supporting the theory of consciousness.
As the translator mentioned in the translator's note at the end, examples of mentioning the legitimacy of a theory through 'axiomatic systematization' are rare these days, but Koch explains that he attempted 'axiomatic systematization' to show how meticulous the integrated information theory is, just like Newton's 'Mathematical Principles of Natural Philosophy'.


How does the brain generate subjective (conscious) experiences?
What is experience?

- All animals 'experience' the spectacle of life.
- No program model can have 'experience'.

[Conscious] experience has five undeniable properties.
First, experience essentially “exists in itself” without an observer (the immanent existence postulate).
Second, any experience is “structured.”
The sensory aspects, including hearing, smell, feeling and emotion, are intricately interwoven.
The structure of this experience has a physical basis in synapses, neurons, and brain activation (constitutive postulate).
Third, any experience is highly informative and rich in “specific content” (information postulate).
Fourth, the experience is integrative.
Although we can describe an experience by breaking it down into its components, the actual experience is experienced as “the whole, including my body” (integration postulate).
Fifth, any experience is “limited in content and time and space.”
What happens outside of me is excluded from my experience (exclusion postulate).


In this way, the five postulates of experience serve as the foundation that enables integrated information theory.
This leads them to infer that all animals experience the sights and sounds of life, and, contrary to conventional wisdom, argues that no program model can have true experience and consciousness.
Even a perfect software model of the brain claims that there is no consciousness.
The author questions, “Why aren’t astrophysicists simulating black holes sucked into supercomputers?”
If their models are so faithful to reality, one might ask, why doesn't spacetime close around the computer they're modeling, and why don't black holes form?
That is because ‘existence’ is not a calculation.
Through the integrated information theory, Koch makes it clear that consciousness is a 'realm of nature' and that consciousness is about 'existence'.

“A computer treated as a mechanism has subtle inherent cause-and-effect forces at the level of metal, at the level of transistors, capacitors, wires, etc.
However, computers do not exist as a whole, but only as small pieces.
And this is equally true whether you are simulating a black hole or a brain.” (p. 292)

Analyzing and quantifying consciousness
mathematical model

Integrated information theory proposes a 'mathematical model' for analyzing consciousness.
This ultimately explains why a physical system called the brain is involved in consciousness.
According to Koch's integrated information theory, the system's "consciousness" (what it is subjectively) is correlated with the system's "causal power" (what it is objectively).
Therefore, it is possible to explain the conscious experience of a physical system by unfolding the full “causal powers [properties]” of the physical system.
This can also be seen this way.
“If you have causal power, even if it is weak, you have consciousness.” “If you replicate causal power, consciousness follows.”

Integrated information theory is a quantitative, rigorous, consistent, and empirically testable theory that begins with experience and progresses to basic neural mechanisms, revealing that it can quantify (reduce) the degree to which a system [organism], whether simple or complex, is determined by its past state and thus its “intrinsic causal power”—that is, the extent to which its future can be influenced by its past state.
The greater the integrated information of a system [living thing], quantified by Φ (pi or phi), the higher the level of consciousness of that system.
In cases where there is no causal power in itself, such as in the case of a neural network that forms the basis of machine learning (in the case of a feedforward network structure), Φ is 0.
In other words, the maximum integrated information value is 0, so there is no consciousness.

Matthew Owen, a professor at the University of Michigan's Center for Consciousness Science, says:
“The greatest strength of integrated information theory is that it is a theoretical approach that makes its basic philosophical commitments ‘explicit.’
While we may disagree with specific commitments, it is undeniable that this approach is very useful for analyzing such commitments and their epistemic role.
Philosophers will undoubtedly debate the philosophical content of 『The Sense of Life Itself』.
But even the most ardent philosophical opponents must acknowledge that this content has a prominent and important role to play in the integrated information theory approach to the study of consciousness.
In this book, Koch makes clear the interdisciplinary nature of consciousness studies while simultaneously addressing a wide range of timeless and timely issues in an accessible manner.” (From a review of this book, “Conscious Matter and Matters of Conscience”)

A 'Philosophical Question' for All Wholes
A Scientific Mission to Develop the Perfect Consciousness Meter

As Matthew Owen has argued in his defense of Koch's theoretical orientation, this explicit commitment (approach) is a very powerful strength of the theory, but it has also been a point of criticism from philosophers as well as scientists.
However, it is regrettable to simply state that this is a limitation of the theorization (quantification) of panpsychism.
Rather, it can be seen as a paradigm shift that boldly expands the scientific horizon.
Koch called the 'physical mechanism of consciousness' the Whole (a concept expressed poetically with a capital W).
By focusing on the senses and 'experience' itself possessed by each living being, we finally reach panpsychism and overcome the limitations of panpsychism with a specific mathematical model theory (Chapter 11: Does consciousness have a function?, Chapter 12: Consciousness and computationalism, Chapter 13: Why computers cannot have experiences).
The process is philosophical and poetic, but also engineering and scientific.


The author says:
According to the integrated information theory, mammals, reptiles, amphibians, birds, and even invertebrates such as insects, octopuses, single-celled microorganisms, and bacteria are conscious.
Plants may also be conscious.
Therefore, the moral status of all subjects (living beings) must be accepted.
“How to cure the narcissism of humanity (human exceptionalism)?”
This question extends to the following aspiration:
“If only we could perfectly measure consciousness!” the author made a public bet with journalist Per Snafrud, confident that research on a perfect consciousness-measuring device would be completed by the end of 2028. (p. 204) Through clinical case studies of brain-damaged patients with impaired consciousness, Koch empathizes with their “despair of being cut off from the world” and advocates for the welfare of fish.
They argue that humans should be held accountable for the cruelty of catching fish with live, wriggling bait and then painfully suffocating them to death.


“Integrated information theory provides a precise answer to the question of who can experience.
Anything whose maximum integrated information value is not 0, anything that has intrinsic causal power, is a complete thing.
What that whole feels, that is, what experience is, is given by a maximally irreducible cause-effect structure.
It exists in itself, has an internal perspective, and is somewhat irreducible.
And that means that there are countless perfections.” (p. 308)

The Path Forward for Consciousness Science

How widespread is consciousness throughout the universe? According to integrated information theory, [conscious] experience could exist in all animals, large and small, bacteria, atoms, perhaps even plants and "inanimate objects," even in unexpected places.
The ethical context of integrated information theory allows us to recognize that humans are not at the center of the universe, nor is nature suited to human purposes.
In keeping with this, Christoph Koch, who cherishes all things, has deep affection for his pets, and lives a life of vegetarianism based on his beliefs after studying consciousness, is a well-mannered scientist who lives a life befitting his theories.

This book addresses the problem of consciousness by relying on the two theories pursued by the author, the Neural Correlates of Consciousness (NCC) and the Integrated Information Theory (IIT), but it is a book that raises rich questions that enhance the scientific understanding of consciousness based on these theories.
By meticulously covering interesting topics related to consciousness, such as the problem of consciousness and non-consciousness (p. 57), other related problems such as consciousness and attention (p. 88), quantum mechanics and consciousness (p. 143), consciousness and biology, especially the problem related to evolution (p. 237), and the relationship with panpsychism (p. 315), it reminds us of the fierce challenge of science that is not bound by limitations.
This will provide an important starting point for suggesting the path forward for consciousness science, a path that explores what consciousness is through reflective thinking.