Appendix D
A note before the list, because the list is uncomfortable to write and likely to be uncomfortable to read.
This book has, over the course of twenty-one chapters and several appendices, said a number of things. It has also, in the course of saying those things, deliberately not said a number of other things that, on a different conception of what this book was for, it would have said. The omissions are not oversights. The omissions are choices. Some of the choices are about the writer's lane. Some of the choices are about the book's scope. Some of the choices are about the limits of the metaphor the book is built on. All of them are worth naming, because a book that does not acknowledge its omissions is, in technical terms, doing the same thing Chapter 16 warned against, which is mistaking the compression for the source.
What follows is, in order of importance, a list of the major things this book did not say, with a brief note about why, and a short pointer toward where to look if you need what this book did not provide. The pointers are not exhaustive. They are the directions I would point a friend.
A reading instruction. If, as you read this appendix, you find yourself thinking I needed this book to say that, please take the thought seriously. The book is what the book is. If what you needed was elsewhere, the appendix is, in part, a map of where elsewhere is. Use it accordingly.
Omission one
Psychiatric medication.
This book has not, at any point, named or recommended any psychiatric medication. The omission is deliberate. I am not a psychiatrist. I have not, myself, taken psychiatric medication, although I have lived through periods in which I should probably have been offered it. Writing about medication without the clinical credentials would, in my honest estimation, be irresponsible, regardless of how much I have read on the subject.
I want to be specific about what this silence does and does not mean. The silence is not an argument against medication. The silence is not a claim that medication is for weaker people. The silence is not the suggestion that mathematics, or any other intellectual tool, is a sufficient substitute for clinical psychiatric care. I have known many people, including people I love, whose lives have been substantially improved by the right medication, prescribed by a competent clinician, taken consistently. The silence in this book is, on inspection, a piece of professional restraint, not a piece of opinion.
If you are reading this book and have been wondering whether to seek a psychiatrist, please understand that the question is not whether you are bad enough to need one. The question is whether your life has been measurably worse than it could be, for long enough that a competent clinician should have a look. The answer, for many people who read books like this, is yes. Talk to a doctor. The mathematics will still be here when you come back.
Omission two
Religion, spirituality, and the contemplative traditions.
This book is profoundly secular. It does not, at any point, draw on Buddhism, Hinduism, Christianity, Islam, Judaism, Stoicism, Sufism, or any of the other traditions that have, over thousands of years, had a great deal to say about exactly the topics this book has covered. The omission is, in part, a function of the writer's own situation: I am not religious, and writing inside a tradition I do not belong to would be the worst kind of intellectual tourism. The omission is also, in part, the deliberate choice to stay in a single lane and not borrow authority from frameworks the book does not, in fact, use.
I want to be clear that this is not a claim that the contemplative traditions are unhelpful. Many of the most useful descriptions of anxious cognition ever written exist inside Buddhist literature. The idea that suffering arises from clinging is, on inspection, the same observation as Chapter 6's argument about asymptotic chasing, expressed two and a half thousand years earlier. The Stoics, in particular Marcus Aurelius and Epictetus, wrote about the difference between what is in your control and what is not in ways that map almost exactly onto the operational consequences of several Part-two chapters. If those traditions speak to you, the book has not been arguing against them. The book has, more narrowly, not been drawing on them.
If you want a serious entry point, I would recommend the Pali canon's Dhammapada for Buddhism, the Bhagavad Gita for the Hindu tradition, Marcus Aurelius's Meditations for Stoicism, and Thomas Merton for a contemplative Christian voice. None of these is what this book has been doing. All of them have been doing useful work in adjacent rooms for longer than mathematics has existed as a discipline.
Omission three
Specific schools of therapy beyond Transactional Analysis.
The book has acknowledged Anna Chandy and Transactional Analysis, in Chapter 5 and again in the interlude, because that is the practice that helped me. The book has not, at any point, discussed cognitive behavioural therapy, dialectical behaviour therapy, internal family systems, eye movement desensitization and reprocessing, somatic experiencing, psychodynamic therapy, narrative therapy, or any of the dozens of other modalities that have helped many people.
This is not because I think these other approaches do not work. Many of them work well, often for specific kinds of problems that TA, alone, would not be the best fit for. CBT, in particular, has the largest evidence base of any therapy modality currently in practice, and the chapters in this book on testing your own behavioural changes are, on inspection, drawing on intellectual ancestors who include several of CBT's founders.
The reason the book stayed in one lane is that I cannot honestly write about modalities I have not personally experienced. If you are looking for a therapist, the modality matters less than the fit. A competent therapist in a modality you respect, working with you regularly, will help more than the theoretical best modality with a clinician you cannot stand. Pick the person first. The framework is the second decision.
Omission four
Particular clinical diagnoses.
This book has used the word anxiety as if it referred to a single recognizable phenomenon. In clinical terms, this is a simplification. There are anxiety disorders that have specific diagnostic criteria and specific treatment implications: generalized anxiety disorder, panic disorder, obsessive-compulsive disorder, post-traumatic stress disorder, social anxiety disorder, specific phobia, and others. They share some features with the general low-grade hum that this book has been describing, and they differ from it in important ways.
I have deliberately not gone into the specific diagnostic criteria, because the book is not a diagnostic tool, and pretending otherwise would be a form of malpractice. If, while reading this book, you have recognized your own experience in a way that goes beyond what the book has described, please understand that the recognition may be evidence that you are dealing with something more specific than the general anxious cognition this book is built around. A clinical assessment is, in those cases, useful. The DSM, the ICD, and a competent clinician will produce a more precise diagnosis than this book has the authority to offer.
For PTSD in particular, including complex PTSD, the book has been gentle in places where a more direct treatment of the topic would have been more useful for some readers. Bessel van der Kolk's The Body Keeps the Score, despite some controversies about specific claims, is the popular entry point most people use, and is worth reading carefully. Judith Herman's Trauma and Recovery is the older, more clinically rigorous text.
Omission five
The body.
This book has been, with one or two small exceptions, a book about the mind. The body has been treated, in technical terms, as the hardware on which the mind runs. This is a serious simplification. Anxiety, in the actual living organism, is not a purely cognitive phenomenon. It is a state of the entire nervous system, with measurable physiological correlates, and it responds, often dramatically, to interventions that have nothing to do with thinking.
The book has not discussed the vagus nerve, the parasympathetic nervous system, polyvagal theory, breath work, somatic practices, yoga in its therapeutic forms, exercise as an anti-depressant, or the specific physiological effects of cold exposure, sunlight, sleep architecture, or gut microbiome composition. All of these have legitimate research behind them, varying in quality, and several of them have helped many people more than any purely cognitive intervention would have. I have not discussed them because I do not have the credentials to discuss them well, and because the book had to be the book it could be rather than the book it would have needed to be to cover everything.
If you are looking for the missing piece, the body is often where it is. A good general practitioner, a competent physiotherapist, a yoga teacher in one of the older traditional schools, a swimming pool, or a long walk in the morning sun will, in many cases, do work that this book has not been built to do.
Omission six
Addiction.
This book has, in passing, mentioned my father, who drank, gambled, and had compulsive patterns of behaviour that, in modern clinical language, would be called addiction. The book has not, at any point, treated addiction as its own subject. The omission is partly personal: I have, by a combination of biology and family history, avoided alcohol and similar dependencies, and writing about something I have not lived would be the wrong move.
The omission is also structural. Addiction has its own enormous literature, its own well-established recovery communities, and its own specific mechanisms that are related to but distinct from the cognitive patterns this book has described. If you are dealing with addiction, in yourself or in someone you love, the book has not been your best resource. Alcoholics Anonymous and its descendant programs have, despite their imperfections, helped more people than any other single framework in the history of addiction recovery. Maia Szalavitz's Unbroken Brain is the most useful single book I have read on the modern science of addiction.
Omission seven
The cultural framings I did not engage with.
This book is written by an Indian man, living in Bangalore, in English, for an English-reading audience. It does not, despite the author's location and background, engage in any sustained way with Indian intellectual traditions about mind, suffering, and the self. The omission is, in part, a function of who I am. I was educated in English, I read in English, the writers who shaped me wrote in English, and I would not be able to write about Indian intellectual traditions with the precision the book has tried to bring to everything else.
The omission is also a piece of honesty about my own deracination. I am, in many ways, a man whose interior life has been formed by Western popular science writing of the late twentieth century, more than by the older traditions of the country I live in. This is not, in my view, something to apologize for. It is also not something to pretend is the only way to write about these subjects. The Indian reader who has come to this book expecting it to draw on Vedanta, on Buddhist psychology, on the Yoga Sutras, on the long tradition of self-knowledge that this culture has been refining for three thousand years, will, on inspection, find that the book did not deliver on that expectation. The reader is entitled to their disappointment.
If you are looking for a serious treatment of mind and anxiety inside Indian frameworks, the Yoga Sutras of Patanjali, particularly with a good modern commentary, are a starting point. Edwin Bryant's translation and commentary is the one I would recommend. The Buddhist Pali sources, again with good commentary, are another. The book in your hands is not a substitute for these. It is, on inspection, written from a different intellectual address.
Omission eight
The limits of the mathematical metaphor itself.
I want to close the appendix with the most uncomfortable omission, which is that the entire premise of this book is a metaphor, and metaphors have limits.
The mind is not, in any literal sense, a computer. The mind shares some features with a computer, and the features it shares are the ones this book has been exploiting. The mind also has features that no computer has and no current computer science describes well: embodiment, continuous interaction with a chemical environment, emergent properties that arise from the specific biological substrate, and several other things we do not, at the present state of neuroscience, understand well enough to model.
The book has, throughout, used mathematical and computational metaphors as if they were the right level of description for the phenomena being discussed. In many cases I believe they are. In some cases they are at best a useful approximation, and in some cases they may, on inspection, be the wrong frame entirely. The reader who finishes this book and feels that the metaphor has been, for them, less useful than I have been claiming, is, in those moments, in possession of a piece of information the book has not been able to offer them: the limits of its own approach.
Other frames exist. Some of them have been mentioned in this appendix. Others have not. The reader who has read carefully through twenty-one chapters of mathematical analogy and concluded that, for them, the analogy is not what helps, has not failed the book. The book has, in their case, failed them, and the appropriate response is to put it down and find a different book. There are many. Some of them are listed in Appendix C. Many more are not, and you will find them in the way readers always do, which is by going looking.
This is, more or less, the list. There are smaller omissions I have not catalogued, because the catalogue would, by the rules of this appendix, never end. There are, on inspection, infinitely many things this book did not say. I have listed the ones I think most readers would notice. The rest, like all the books not mentioned in Appendix C, are out there, in their proper places, doing the work the book in your hands was not equipped to do.
I want to make one closing observation, because the appendix would be incomplete without it. The honest acknowledgment of what a book did not do is, in some quiet way, the most respectful thing the book can offer the reader. The book that pretends to be complete is, on inspection, doing the reader a small disservice, because completeness is not, in any human work, achievable. The acknowledgment of incompleteness is, in technical terms, the same thing as the acknowledgment of compression in Chapter 16. The book is a compression. The compression has costs. The costs are the things the compression discarded. Naming them is the least I can do, having decided, for whatever good or bad reasons, to leave them out.
What you needed, the book may not have provided. That is alright. The needing is a piece of information about you. The not-providing is a piece of information about the book. Both pieces of information are useful. Take them both, and go on.