Prologue: The World Inside Our Heads

Part 1: Irrationality

Chapter 1: Close yet far
John M.'s Hacked Smartphone · Helen S.'s World Crumbling Down · The Confidence of Old Lady Margaret G. · A Delusion So Normal? · The Deep Furrow Between Sanity and Abnormality · Not Insane? What Does It Mean? · Where Does Social Division Begin?

Chapter 2: The Illusion of Rationality
What kind of certainty are we talking about? · What is delusion? · The dry well of absolute truth · Minimal rationality · The irrationality of 'normal' certainty · How rational are we? · Cognitive distortions

Chapter 3: Why does schizophrenia occur?
Schizophrenia: A History of Diagnosis · Is Schizophrenia a Disease? · Schizophrenia Research · Where Do Demons Come From: The Role of Genetics · Why Schizophrenia Exists · The Evolutionary Paradox of Schizophrenia · Genius and Madness Connect · The Continuity Hypothesis

Chapter 4: The Evolution of Irrationality
The correlation between irrationality and survival, irrationality as an appendix, error management, quick and simple, the positive effects of positive illusions, irrationality in forming social belonging, communication through conviction, natural selection is not interested in truth.

Part 2: Prediction Machine

Chapter 5: We Create the World
Uncertainty, the alien perspective, the inverted black box problem, a neuroscientific perspective, an alternative neuroscientific perspective, the brain as a prediction machine, a glimpse into neuroscience: predictive processing, uncertainty, and controlling accuracy, the pinnacle of the prediction hierarchy, highly accurate predictions: certainty, and processing irrational predictions, I create a world that suits my preferences.

Chapter 6: People Who Lost Their Balance
People who can see concave faces · Eye movements at ball height · Regularity is the mother of all predictions · The explanatory gap between neurobiology and subjective experience · The brain's volume control · The consequences of imbalance: abnormal salience and the development of delusions · On the 'uncorrectability' of delusions · A pragmatic interpretation of delusions · Top-down hierarchical predictive processing · A new look at confirmation bias · Confirmation bias in perception and thought · The dotted cloud and the two illusions

Chapter 7 Who is the sick person here?
Are delusions adaptive? · Paranoia as fire alarms and shear bolts · Are conspiracy theories truly delusional? · What conspiracy theory beliefs and delusions have in common · The difference between conspiracy theory beliefs and delusions · The cognitive irrationality that we cannot help but fall for

Chapter 8: Opportunities, Risks, and Side Effects
What Our Brain Does·Existence is not a ought·Conviction is a hypothesis·De-stigmatization, between the not understood and the incomprehensible·What am I certain of?

Epilogue: Confidence in the Pandemic Era

Acknowledgements
Translator's Note
Glossary of terms
Americas
References

“Is reason really rational?”
In an age of post-truth, conspiracy theories, information overload, and extremes
A book that questions whether what you see and believe is truly true.

All humans consider themselves to be 'rational'.
Also, they always consider what they know to be correct and in line with the 'facts'.
So, we easily assume that people who have different thoughts and values ​​than us are wrong and 'irrational'.
But is that really true? Are humans rational? Is what you and I know all there is to know? "The Illusion of Sanity" begins with these questions.
It proves in detail that everything we see, believe, and think is true is in fact nothing more than a kind of 'illusion'.

The author, Philipp Sterzer, is a world-renowned neuroscientist and psychiatrist.
Based on his diverse research experience at the Max Planck Institute for Psychiatry and the Institute of Visual Perception, he was recognized in academic circles for his pioneering research on changes in the perceptual process of schizophrenia.
What he noticed was that there was not much difference in brain function between people we commonly consider “crazy” and normal people, meaning that it was difficult to clearly distinguish between delusional thinking and normal thinking.
The brain, confined to a dark space inside the skull, constructs our image of the world from sensory data (stimuli) that are constantly given to us without our awareness.
This book traces how the brain relies on data to form its worldview, explaining where confidence comes from, how it's maintained, and how it functions.
Crossing the boundaries of philosophy, genetics, social psychology, cognitive psychology, and neuroscience, he delves into the latest brain science theories and his own research from the past decade to uncover the flaws in human reason.


This book became a hot topic, reaching number one on the bestseller list on Amazon Germany immediately after its release and staying there for over two months.
It caused a great stir in society, with praise from the German media.
This is because it completely denied human reason, which we had firmly believed to be rational, and gave many people both insight and considerable shock.
In this age of extremes, this book, which constantly questions what reason we truly need, will become an essential textbook for modern people who are caught up in the illusion of reason.

The Fallacies of Human Reason Revealed by Neuroscience and Psychiatry
Why does everyone think they're right? Why do we feel uncomfortable with opinions that differ from ours?
Beyond philosophical inquiry, trace what happens in the brain!

This book asks questions:
Corona conspiracy theorists, climate skeptics, fake news believers… Why do we fall into such different logic when looking at the same thing? Who is sane, and who isn't? We must be mindful of the fact that even our normal thinking is irrational, that is, we suffer from the illusion of rationality.
The brain constructs a world that seems advantageous and rational to us.
Our perceptions are merely illusions that sometimes correspond more to the world, sometimes less.
The less consistent one is, the further one is from sanity, but the line between normal and abnormal is fluid.

Part 1 examines human irrationality.
It tells the stories of John, who is convinced that the Russian mafia hacked his phone; Helen, a die-hard scientist who feels a second 9/11 has occurred on the New York subway; and Margaret, an elderly woman who believes her son-in-law keeps stealing from her, showing that irrational certainty is not the exception but the rule.
This shows how close 'normal' and 'abnormal', psychologically 'healthy' and 'sick' states are to each other.
Moreover, it reveals that this irrationality is ultimately a strategy for human survival.


Part 2 explores the brain as a prediction machine.
Drawing on scientific case studies and the latest research, it explains why we all live in our own world.
The main theory covered in this book, 'predictive processing', is being introduced for the first time in a popular science book.
In neuroscience and philosophy, it describes an "illusion that is in harmony with reality," and is a theory of brain function that assumes that the brain operates as a generative model, generating data that matches its own predictions based on sensory data.


◆ Why do men think they are better looking and superior than they actually are?
Men tend to overestimate themselves, while women tend to underestimate themselves.
Even most men who consider themselves to be "rational" give themselves a good grade.
The author finds the cause of this irrational thinking in evolutionary fitness.
Because the most important thing for mankind is survival and reproduction.
Men suffer great losses if they miss out on reproductive opportunities.
That's why it evolved in a direction that actively appeals to itself.
It is an extension of this evolution that male peacocks have such flashy feathers that are completely useless and even a nuisance in real life.
On the other hand, women have evolved to minimize the cost of mistakes because they can pay a high price for frequent flirting with the opposite sex, which is pregnancy.
This is why irrationality in men and women's perception is expressed differently.

◆ Why do mothers have no choice but to become hedgehog moms?
Have you ever watched parents overestimate their children's qualities and enthusiastically praise them, and then inwardly squinted? To parents, their children are the most precious thing in the world.
More lovable and precious than anyone else.
For that reason, there are no parents in the world who objectively perceive their children's shortcomings.
It is a kind of positive illusion that stabilizes the relationship with the spouse and makes them take better care of their offspring.
This is also an error in human reason.
The idea that parents overlook their children's weaknesses is a kind of delusion, a result of cognitive bias that appears in order to survive and reproduce well.


◆ Why do humans feel secure when they belong to a group?
Differing beliefs about climate change, evolution, religion, politics, sports, and so on have little to do with how much relevant information is available or how well that knowledge is communicated.
Rather, what matters more is how well such convictions align with the values ​​of the group to which one belongs.
For generations, humans have considered it important to get along well with members of the same species.
Shared beliefs have been useful in excluding dissenters and other groups because they provide the benefit of uniting and solidarizing groups in complex societies.
This is why humans, as social beings, have irrational convictions.


◆ Human instinct to search for rules anytime, anywhere
The brain is a prediction machine, specialized in recognizing repeating patterns.
It is to predict the future.
For example, even when good luck happens several times, we are confident that it will happen again next time, even though it is actually just a coincidence.
The reason the brain, as a prediction machine, functions so smoothly is because the world it tries to predict is, in many ways, quite stable.
Predictions help the brain create perceptions, making it easier to subjectively interpret and predict uncertain situations.
Additionally, when sensory data is uncertain, the brain builds stronger predictions.
This is the principle by which our convictions become stronger.


Why we should be wary of excessive self-confidence
How to coexist peacefully with others

“Convictions are divided into rational and irrational, healthy and sick, but what is clear is that no matter how ‘normal’ or ‘insane’ a conviction may seem, it is all just a hypothesis.
Accepting that your thinking may be wrong and keeping in mind that nothing is absolutely certain can help you be open to different perspectives and understand the world more clearly.” _From the text

While certainty offers conveniences such as reducing complexity, facilitating decision-making, and providing a sense of belonging to a group, it also carries with it negative consequences such as black-and-white thinking, polarization, and dichotomous thinking.
Amidst the many pressing issues facing our time—war, pandemics, climate change—if we show tolerance for one another rather than cling to our own convictions, and if our individual convictions function as hypotheses, we can expand the possibilities for constructive dialogue.


The new perspective on the brain presented in this book helps us critically question our own thinking and gain a clearer understanding of the world.
Now, as you gain confidence, why not ask yourself these questions: "Is what I know all there is? Is it true? What is the basis for my confidence?" In our pluralistic modern society, this kind of correction of thinking will guide us to peacefully coexist with others who hold different views.