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I long ago stopped reading books on note-taking. They were always too vague and boring, full of platitudes that had little to do with the world outside academia. I especially avoided “how-to” style books on the subject.
They would often list dozens of tips and tricks that had little to do with each other. There was never an overarching system for turning notes into concrete results.
But recently I picked up How To Take Smart Notes by Sönke Ahrens. Ahrens is a Lecturer in Philosophy of Education at the University of Duisburg-Essen and also coaches students, academics, and professionals with a focus on time management, decision-making, and personal growth.
It is by far the most impactful and profound book I’ve ever read on the subject. I was astounded to encounter in its pages (with uncanny similarity) many of the same principles I had discovered over 10 years of personal experience.
This book is so full of insights that it broke my usual approach to summarizing books.
My approach is based on the assumption that most books are a few morsels of real insight wrapped in layers and layers of fluff. As I read, I systematically unravel those layers of fluff and extract only those insights, like a chemist distilling only the purest compound.
But this book is not written in the usual way. It is written using an external thinking system, which I call a Second Brain.
The evidence is clear: Instead of squeezing as many pages as possible out of one idea, How To Take Smart Notes squeezes as many ideas as possible onto every page. Every paragraph has a point, and I struggled to leave anything out of this summary.
By identifying the principles that stand the test of time despite huge changes in the underlying technology, we can better understand the essential nature of the creative process. We can focus our efforts on mastering the art of creative note-taking, producing more insightful writing, and fulfilling our full potential.
What the book is about
How To Take Smart Notes is a book on note-taking for students, academics, and non-fiction writers.
It promises to help readers adopt “a reliable and simple external structure to think in that compensates for the limitations of our brains.” By adopting such a system, Ahrens promises that we will be able to “efficiently turn our thoughts and discoveries into convincing written pieces and build up a treasure of smart and interconnected notes along the way.”
While producing published written works is the end goal, is it not the only goal. Ahrens argues convincingly that turning one’s thoughts into writing isn’t just useful for writers but for anyone who wants to improve their thinking and learning in general.
By focusing on writing, Ahrens is able to speak in concrete terms about a specific creative process while simultaneously drawing universal conclusions. Instead of notes becoming a “graveyard for thoughts,” they can become a life-long pool of rich and interconnected ideas we can draw on no matter where our interests lead us.
Ahrens’ approach to note-taking was inspired by the 20th-century German sociologist Niklas Luhmann (1927-1998). Luhmann was a prolific note-taker, writer, and academic. Early in his academic career, Luhmann realized that a note was only as valuable as its context – its network of associations, relationships, and connections to other information.
He developed a simple system based on paper index cards, which he called his “slip-box” (or zettelkasten in German). It was designed to connect any given note to as many different potentially relevant contexts as possible.
Luhmann rejected alphabetical categorization of his notes, along with fixed categories like the Dewey Decimal System. He intended his notes not just for a single project or book but for a lifetime of reading and researching. He designed his slip-box as a research database made up of index cards (zettel) that were “thematically unlimited” and could be infinitely extended in any direction.
Although it appeared to be just a simple filing system made up of index cards, Luhmann’s slip-box grew to become an equal thinking partner in his work. He described his system as his secondary memory (zweitgedächtnis), alter ego, or reading memory (lesegedächtnis). He reported that it continuously surprised him with ideas he’d forgotten he had. Because of this, he claimed that there was actual communication going on between himself and his zettelkasten. As he built up his collection of notes, he embarked on a series of achievements that would eventually make him one of the most influential sociologists and scientists of the 20th century.
Here’s how it worked:
- Luhmann wrote down interesting or potentially useful ideas he encountered in his reading on uniformly sized index cards
- He wrote only on one side of each card to eliminate the need to flip them over, and he limited himself to one idea per card so they could be referenced individually
- Each new index card received a sequential number, starting at 1. When a new source was added to that topic, or he found something to supplement it, he would add new index cards with letters as suffixes (1a, 1b, 1c, etc.)
- These branching connections were marked in red as close as possible to the point where the branch began
- Any of these branches could also have their own branches. The card for fellow German sociologist Jürgen Habermas, for example, was labeled 21/3d26g53
- As he read, he would create new cards, update or add comments to existing ones, create new branches from existing cards, and create new links between cards on different “strands”
This diagram shows how subtopics branched off from main topics:
Not only did this create a system that could extend infinitely in any direction, but it also gave each index card a permanent ID number. This number could be referenced from any other card, because it would never change. The branches created “strands” of thought that one could enter at any point, following it downstream to be elaborated upon or upstream to its source.
It also led to a meaningful topography within the system: Topics that had been extensively explored had long reference numbers, making their length informative on its own. There is no hierarchy in the zettelkasten, which means it can grow internally without any preconceived scheme. By creating notes as a decentralized network instead of a hierarchical tree, Luhmann anticipated hypertext and URLs.
Over his 30-year career, Luhmann published 58 books and hundreds of articles on the way to completing his two-volume masterwork, The Society of Society (1997). It presented a radical new theory that not only changed sociology but also provoked heated discussions in philosophy, education, political theory, and psychology.
For years, the importance of Luhmann’s slip-box was underestimated. As early as 1985, he would regularly point to it as the source of his amazing productivity: “I, of course, do not think everything by myself. It happens mainly within the slip-box” (Luhmann, Baecker, and Stanitzek 1987, 142). Until recently, no one believed that such a simple system could produce such prolific output. We are so used to the idea that great outcomes require great (and complicated) efforts.
But Luhmann often remarked that he never forced himself to do anything he didn’t feel like doing: “I only do what is easy. I only write when I immediately know how to do it. If I falter for a moment, I put the matter aside and do something else” (Luhmann et al., 1987, 154f).
Wouldn’t it make sense that such output over so many years would be possible because it was simple and easy, not in spite of it? Upon his death, Luhmann’s slip-box contained 90,000 notes. This may seem like a staggering number until you realize that it amounts to only six notes per day.
Let’s look deeper at the main principles that Luhmann used in his work, which Ahrens has adapted to the modern age. The explosion of technology and connectivity has inundated us with an overabundance of information. These principles go a long way toward reestablishing the boundaries and constraints that creativity needs to thrive.
Principle #1: Writing is not the outcome of thinking; it is the medium in which thinking takes place
Writing doesn’t begin when we sit down to put one paragraph after another on the screen or page. It begins much, much earlier, as we take notes on the articles or books we read, the podcasts or audiobooks we listen to, and the interesting conversations and life experiences we have.
These notes build up as a byproduct of the reading we’re already doing anyway. Even if you don’t aim to develop a grand theory, you need a way to organize your thoughts and keep track of the information you consume.
If you want to learn and remember something long-term, you have to write it down. If you want to understand an idea, you have to translate it into your own words. If we have to do this writing anyway, why not use it to build up resources for future publications?
Writing is not only for proclaiming fully formed opinions, but for developing opinions worth sharing in the first place.
Writing works well in improving one’s thinking because it forces you to engage with what you’re reading on a deeper level. Just because you read more doesn’t automatically mean you have more or better ideas. It’s like learning to swim – you have to learn by doing it, not by merely reading about it.
The challenge of writing as well as learning is therefore not so much to learn, but to understand, as you will already have learned what you understand. When you truly understand something, it is anchored to a latticework of related ideas and meanings, which makes it far easier to remember.
For example, you could memorize the fact that arteries are red and veins are blue. But it is only when you understand why – that arteries carry oxygen-rich blood from the heart to the rest of the body, while veins carry blood low in oxygen back to the heart – that that fact has any value. And once we make this meaningful connection between ideas, it’s hard not to remember it.
The problem is that the meaning of something is not always obvious. It requires elaboration – we need to copy, translate, re-write, compare, contrast, and describe a new idea in our own terms. We have to view the idea from multiple perspectives and answer questions such as “How does this fact fit with others I already know?” and “How can this phenomenon be explained by that theory?” or “How does this argument compare to that one?”
Completing these tasks is exceedingly difficult inside the confines of our heads. We need an external medium in which to perform this elaboration, and writing is the most effective and convenient one ever invented.
Principle #2: Do your work as if writing is the only thing that matters
The second principle extends the previous one even further: Do you work as if writing is the only thing that matters.
In academia and science, virtually all research is aimed at eventual publication Ahrens notes that “there is no such thing as private knowledge in academia. An idea kept private is as good as the one you never had.”
The purpose of research is to produce public knowledge that can be scrutinized and tested. For that to happen, it has to be written down. And once it is, what the author meant doesn’t matter – only the actual words written on the page matter.
This principle requires us to expand our definition of “publication” beyond the usual narrow sense. Few people will ever publish their work in an academic journal or even on a blog. But everything that we write down and share with someone else counts: notes we share with a friend, homework we submit to a professor, emails we write to our colleagues, and presentations we deliver to clients all count as knowledge made public.
This might still seem like a radical principle. Should we publicize even the ideas we’ve only just encountered, or opinions half-formed, or wild theories we can’t substantiate? Do we really need even more people broadcasting half-baked opinions and theories online?
But the important part is the principle: Work as if writing is the only thing that matters. Having a clear, tangible purpose when you consume information completely changes the way you engage with it. You’ll be more focused, more curious, more rigorous, and more demanding. You won’t waste time writing down every detail, trying to make a perfect record of everything that was said. Instead, you’ll try to learn the basics as efficiently as possible so you can get to the point where open questions arise, as these are the only questions worth writing about.
Almost every aspect of your life will change when you live as if you are working toward publication. You’ll read differently, becoming more focused on the parts most relevant to the argument you’re building. You’ll ask sharper questions, no longer satisfied with vague explanations or leaps in logic. You’ll naturally seek venues to present your work since the feedback you receive will propel your thinking forward like nothing else. You’ll begin to act more deliberately, thinking several steps beyond what you’re reading to consider its implications and potential.
Deliberate practice is the best way to get better at anything, and in this case, you are deliberately practicing the most fundamental skill of all: thinking. Even if you never actually publish one line of writing, you will vastly improve every aspect of your thinking when you do everything as if nothing counts except writing.
Principle #3: Nobody ever starts from scratch
One of the most damaging myths about creativity is that it starts from nothing. The blank page, the white canvas, the empty dance floor: Our most romantic and universal artistic motifs seem to suggest that “starting from scratch” is the essence of creativity.
This belief is reinforced by how writing is typically taught: We are told to “pick a topic” as a necessary first step, then to conduct research, discuss and analyze it, and finally come to a conclusion.
But how can you decide on an interesting topic before you’ve read about it? You have to immerse yourself in research before you even know how to formulate a good question. And the decision to read about one subject versus another also doesn’t appear out of thin air. It usually comes from an existing interest or understanding. The truth is every intellectual endeavor starts with a predicting conception.
This is the tension at the heart of the creative process: You have to research before you pick what you will write about. Ideally, you should start researching long before, so you have weeks and months and even years of rich material to work with as soon as you decide on a topic. This is why an external system to record your research is so critical. It doesn’t just enhance your writing process; it makes it possible.
And all this pre-research also involves writing. We build up an ever-growing pool of externalized thoughts as we read. When the time comes to produce, we aren’t following a blindly invented plan plucked from our unreliable brains. We look in our notes and follow our interests, curiosity, and intuition, which are informed by the actual work of reading, thinking, discussing, and taking notes. We never again have to face that blank screen with the impossible demand of “thinking of something to write about.”
No one ever really starts from scratch. Anything they come up with has to come from prior experience, research, or other understanding. But because they haven’t acted on this fact, they can’t track ideas back to their origins. They have neither supporting material nor accurate sources. Since they haven’t been taking notes from the start, they either have to start with something completely new (which is risky) or retrace their steps (which is boring).
It’s no wonder that nearly every guide to writing begins with “brainstorming.” If you don’t have notes, you have no other option. But this is a bit like a financial advisor telling a 65-year-old to start saving for retirement – too little, too late.
Taking notes allows you to break free from the traditional, linear path of writing. It allows you to systematically extract information from linear sources, mix and shake them up together until new patterns emerge, and then turn them back into linear texts for others to consume.
You’ll know you’ve succeeded in making this shift when the problem of not having enough to write about is replaced by the problem of having far too much to write about. When you finally arrive at the decision of what to write about, you’ll already have made that decision again and again at every single step along the way.
Principle #4: Our tools and techniques are only as valuable as the workflow
Just because writing is not a linear process doesn’t mean we should go about it haphazardly. We need a workflow – a repeatable process for collecting, organizing, and sharing ideas.
Writing is often taught as a collation of “tips and tricks” – brainstorm ideas, make an outline, use a three-paragraph structure, repeat the main points, use vivid examples, set a timer. Each one in isolation might make sense, but without the holistic perspective of how they fit together, they add more work than they save. Every additional technique becomes its own project without bringing the whole much further forward. Before long, the whole mess of techniques falls apart under its own weight.
It is only when all the work becomes part of an integrated process that it becomes more than the sum of its parts. Even the best techniques won’t make a difference if they are used in conflicting ways. This is why the slip-box isn’t yet another technique. It is the system in which all the techniques are linked together.
Good systems don’t add options and features; they strip away complexity and distractions from the main work, which is thinking. An undistracted brain and a reliable collection of notes is pretty much all we need. Everything else is just clutter.
Principle #5: Standardization enables creativity
Ahrens uses the excellent analogy of how the invention of shipping containers revolutionized international trade to demonstrate the role of note-taking in modern writing
Container shipping is a simple idea: ship products in standardized containers instead of loading them onto ships haphazardly as had always been done. But it took multiple failed attempts before it was successful because it wasn’t actually about the container, which after all is just a box.
The potential of the shipping container was only unleashed when every other part of the shipping supply chain was changed to accommodate it. From manufacturing to packaging to final delivery, the design of ships, cranes, trucks, and harbors all had to align around moving containers as quickly and efficiently as possible. Once they did, international shipping exploded, setting the stage for Asia to become an economic power among many other historic changes.
Many people still take notes, if at all, in an ad-how, random way. If they see a nice sentence, they underline it. If they want to make a comment, they write it in the margins. If they have a good idea, they write it in whichever notebook is close at hand. And if an article seems important enough, they might make the effort to save an excerpt. This leaves them with many different kinds of notes in many different places and formats. This means when it comes time to write, they first have to undertake a massive project to collect and organize all these scattered notes.
Notes are like shipping containers for ideas. Instead of inventing a new way to take notes for every source you read, use a completely standardized and predictable format every time. It doesn’t matter what the notes contain, which topic they relate to, or what medium they arrived through – you treat each and every note exactly the same way.
It is this standardization of notes that enables a critical mass to build up in one place. Without a standard format, the larger the collection grows, the more time and energy have to be spent navigating the ever-growing inconsistencies between them. A common format removes unnecessary complexity and takes the second-guessing out of the process. Like LEGOs, standardized notes can easily be shuffled around and assembled into endless configurations without losing sight of what they contain.
The same principle applies to the steps of processing our notes. Consider that no single step in the process of turning raw ideas into finished pieces of writing is particularly difficult. It isn’t very hard to write down notes in the first place. Nor is turning a group of notes into an outline very demanding. It also isn’t much of a challenge to turn a working outline full of relevant arguments into a rough draft. And polishing a well-conceived rough draft into a final draft is trivial.
So if each individual step is so easy, why do we find the overall experience of writing so grueling? Because we try to do all the steps at once. Each of the activities that make up “writing” – reading, reflecting, having ideas, making connections, distinguishing terms, finding the right words, structuring, organizing, editing, correcting, and rewriting – require a very different kind of attention.
Proofreading requires very focused, detail-oriented attention, while choosing which words to put down in the first place might require a more open, free-floating attention. When looking for interesting connections between notes, we often need to be in a playful, curious state of mind, whereas when putting them in logical order, our state of mind probably needs to be more serious and precise.
The slip-box is the host of the process outlined above. It provides a place where distinct batches of work can be created, worked on, and saved permanently until the next time we are ready to deploy that particular kind of attention. It deliberately puts distance between ourselves and what we’ve written, which is essential for evaluating it objectively. It is far easier to switch between the role of creator and critic when there is a clear separation between them, and you don’t have to do both at the same time.
By standardizing and streamlining both the format of our notes and the steps by which we process them, the real work can come to the forefront: thinking, reflecting, writing, discussing, testing, and sharing. This is the work that adds value, and now we have the time to do it more effectively.
Principle #6: Our work only gets better when exposed to high-quality feedback
A workflow is similar to a chemical reaction: It can feed on itself, becoming a virtuous cycle where the positive experience of understanding a text motivates us to take on the next task, which helps us get better at what we’re doing, which in return makes it more likely for us to enjoy our work, and so on.
Nothing motivates us more than becoming better at what we do. And we can only become better when we intentionally expose our work to high-quality feedback.
There are many forms of feedback, both internal and external – from peers, from teachers, from social media, and from rereading our own writing. But notes are the only kind of feedback that is available anytime you need it. It is the only way to deliberately practice your thinking and communication skills multiple times per day.
It is easy to think we understand a concept until we try to put it in our own words. Each time we try, we practice the core skill of insight: distinguishing the bits that truly matter from those that don’t. The better we become at it, the more efficient and enjoyable our reading becomes.
Feedback also helps us adjust our expectations and predictions about how much we can get done in an hour or a day. Instead of sitting down to the amorphous task of “writing,” we dedicate each working session to concrete tasks that can be finished in a reasonable timeframe: Write three notes, review two paragraphs, check five sources for an essay, etc. At the end of the day, we know exactly how much we accomplished (or didn’t accomplish) and can adjust our future expectations accordingly.
Principle #7: Work on multiple, simultaneous projects
It is only when you have multiple, simultaneous projects and interests that the full potential of an external thinking system is realized.
Think of the last time you read a book. Perhaps you read it for a certain purpose – to gain some familiarity with a topic you’re interested in or find insights for a project you’re working on. What are the chances that the book contains only the precise insights you were looking for and no others? Extremely low it would seem. We encounter a constant stream of new ideas, but only a tiny fraction of them will be useful and relevant to us at any given moment.
Since the only way to find out which insights a book contains is to read it, you might as well read and take notes productively. Spending a little extra time to record the best ideas you encounter – whether or not you know how they will ultimately be used – vastly increases the chances that you will “stumble upon” them in the future.
The ability to increase the chances of such future accidental encounters is a powerful one because the best ideas are usually ones we haven’t anticipated. The most interesting topics are the ones we didn’t plan on learning about. But we can anticipate that fact and set our future selves up for a high probability of productive “accidents.”
Principle #8: Organize your notes by context, not by topic
Now that you’ve been collecting notes on you’re reading, how should you organize them?
The classic mistake is to organize them into ever more specific topics and subtopics. This makes it look less complexbut quickly becomes overwhelming. The more notes pile up, the smaller and narrower the subtopics become, limiting your ability to see meaningful connections between them. With this approach, the greater one’s collection of notes, the less accessible and useful they become.
Instead of organizing by topic and subtopic, it is much more effective to organize by context. Specifically, the context in which it will be used. The primary question when deciding where to put something becomes “In which context will I want to stumble upon this again?”
In other words, instead of filing things away according to where they came from, you file them according to where they’re going. This is the essential difference between organizing like a librarian and organizing like a writer.
A librarian asks “Where should I store this note?” Their goal is to maintain a taxonomy of knowledge that is accessible to everyone, which means they have to use only the most obvious categories. They might file notes on a psychology paper under “misjudgments,” “experimental psychology,” or “experiments.”
That works fine for a library, but not for a writer. No pile of notes filed uniformly under “psychology” will be easy to turn into a paper. There is no variation or disagreement from which an interesting argument could arise.
A writer asks “In which circumstances will I want to stumble upon this note?” They will file it under a paper they are writing, a conference they are speaking at, or an ongoing collaboration with a colleague. These are concrete, near-term deliverables, and not abstract categories.
Organizing by context does take a little bit of thought. The answer isn’t always immediately obvious. A book about personal finance might interest me for completely different reasons if I am a politician working on a campaign speech, a financial advisor trying to help a client, or an economist developing monetary policy. If I encounter a novel engineering method, it may be useful for completely different reasons depending on whether I am working on an engineering textbook, a skyscraper, or a rocket booster.
Writers don’t think about a single, “correct” location for a piece of information. They deal in “scraps” which can often be repurposed and reused elsewhere. The discarded byproducts from one piece of writing may become the essential pillars of the next one. The slip-box is a thinking tool, not an encyclopedia, so completeness is not important. The only gaps we do need to be concerned about are the gaps in the final manuscript we are working toward.
By saving all the byproducts of our writing, we collect all the future material we might need in one place. This approach sets up your future self with everything they need to work as decisively and efficiently as possible. They won’t need to trawl through folder after folder looking for all the sources they need. You’ll already have done that work for them.
Principle #9: Always follow the most interesting path
Ahrens notes that in most cases, students fail not because of a lack of ability, but because they lose a personal connection to what they are learning:
“When even highly intelligent students fail in their studies, it’s most often because they cease to see the meaning in what they were supposed to learn (cf. Balduf 2009), are unable to make a connection to their personal goals (Glynn et al. 2009) or lack the ability to control their own studies autonomously and on their own terms (Reeve and Jan 2006; Reeve 2009).”
This is why we must spend as much time as possible working on things we find interesting. It is not an indulgence. It is an essential part of asking our work sustainable and thus successful.
This advice runs counter to the typical approach to planning we are taught. We are told to “make a plan” upfront and in detail. Success is then measured by how closely we stick to this plan. Our changing interests and motivations are to be ignored or suppressed if they interfere with the plan.
The history of science is full of stories of accidental discoveries. Ahrens gives the example of the team that discovered the structure of DNA. It started with a grant, but not a grant to study DNA. They were awarded funds to find a treatment for cancer. As they worked, the team followed their intuition and interest, developing the actual research program along the way (Rheinberger 1997). If they stuck religiously to their original plan, they probably wouldn’t have discovered a cure for cancer and certainly wouldn’t have discovered the structure of DNA.
Plans are meant to help us feel in control. But it is much more important to actually be in control, which means being able to steer our work towards what we consider interesting and relevant. According to a 2006 study by psychology professor Arlen Moller, “When people experienced a sense of autonomy with regard to the choice [of what to work on], their energy for subsequent tasks was not diminished” (Moller 2006, 1034). In other words, when we have a choice about what to work on and when, it doesn’t take as much willpower to do it.
Our sense of motivation depends on making consistent forward progress. But in creative work, questions change and new directions emerge. That is the nature of insight. So we don’t want to work according to a rigid workflow that is threatened by the unexpected. We need to be able to make small, constant adjustments to keep our interest, motivation, and work aligned.
By breaking down the work of writing into discrete steps, getting quick feedback on each one, and always following the path that promises the most insight, unexpected insights can become the driving force of our work.
Luhmann never forced himself to do anything and only did what came easily to him: “When I am stuck for one moment, I leave it and do something else.” As in martial arts, if you encounter resistance or an opposing force, you should not push against it but instead redirect it towards another productive goal.
Principle #10: Save contradictory ideas
Working with a slip-box naturally leads us to save ideas that are contradictory or paradoxical.
It’s much easier to develop an argument from a lively discussion of pros and cons rather than a litany of one-sided arguments and perfectly fitting quotes.
Our only criterion for what to save is whether it connects to existing ideas and adds to the discussion. When we focus on open connections, disconfirming or contradictory data suddenly becomes very valuable. It often raises new questions and opens new paths of inquiry. The experience of having one piece of data completely change your perspective can be exhilarating.
The real enemy of independent thinking is not any external authority, but our own inertia. We need to find ways to counteract confirmation bias – our tendency to take into account only information that confirms what we already believe. We need to regularly confront our errors, mistakes, and misunderstandings.
By taking notes on a wide variety of sources and in objective formats that exist outside our heads, we practice the skill of seeing what is really there and describing it factually. By saving ideas that aren’t compatible with each other and don’t necessarily support what we already think, we train ourselves to develop subtle theories over time instead of always jumping to conclusions.
By playing with a concept, stretching and reconceiving and remixing it, we become less attached to how it was originally presented. We can extract certain aspects or details for our own uses. With so many ideas at our disposal, we are no longer threatened by the possibility that a new idea will undermine existing ones.
Don’t just feel smarter. Become smarter.
Working with a slip-box can be disheartening, because you are constantly faced with the gaps in your understanding. But at the same time, it increases the chances that you will actually move the work forward.
Our choice then is whether we want to feel smarter or become smarter.
Students in most educational institutions are not encouraged to independently build a network of connections between different kinds of information. They aren’t taught how to organize the very best and most relevant knowledge they encounter in a long-term way across many topics. Most tragically of all, they aren’t taught to follow their interests and take the most promising path in their research.
Ultimately, learning should not be about hoarding stockpiles of knowledge like gold coins. It is about becoming a different kind of person with a different way of thinking. The beauty of this approach is that we co-evolve with our slip-boxes: We build the same connections in our heads as we deliberately develop them in our slip-box. Writing then is best seen not only as a tool for thinking but as a tool for personal growth.