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Book Notes: “How to Take Smart Notes” by Sönke Ahrens


How to Take Smart Notes by Sönke Ahrens (2017) is a book that lays out the rationale and the methods behind the zettelkasten note-taking system (also referred to as the “slip box” method). Zettelkasten is a simple but powerful way of recording, organizing and generating insights from what we read and learn. It provides a way of saving ideas by writing them down as notes, creating connections between those ideas, and using your accumulated notes to write productively (articles, dissertations, books, etc.). Mind you, the zettelkasten is not a productivity system in the way that David Allen’s Getting Things Done system is. Zettelkasten shares some qualities of the GTD methodology (particularly where it comes to offloading or freeing up mental capacity by recording important information), but the target audience for the book is the academic researcher, doctoral student and non-fiction writer. Zettelkasten is designed for the capture, processing, and publication of ideas.

The zettelkasten method is relatively straight-forward. Ahrens describes the process in detail in Chapter 2. First, the practitioner generates temporary notes while thinking, learning, and reading. These temporary notes are carefully considered: if the temporary note is deemed sufficiently interesting it is rewritten—with future utility and retrieval in mind—and archived in the zettelkasten as a permanent note (temporary notes that don’t warrant saving are discarded). A key feature of the system is that permanent notes are limited to a single idea per index card.

Permanent notes are not organized via a top-down approach (such storing notes in category-specific silos). Instead, notes are commingled in a single repository with your other notes. Keywords, cross-references and index notes (notes that serve as entry-points to clusters of related ideas) can be used to link notes that are related by topic, category or idea. The goal is to create a level of atomicity and abstraction that encourages connection and exploration with other ideas recorded in the note-taking system. Over time, the practice should result in dense network of interlinked ideas. At this point, the author assures us, it is a relatively straight-forward process to transition from notes to draft manuscript to publication.

On the face of it, How to Take Smart Notes is a book about taking notes (thrilling topic for most people, I’m sure!), but really it’s about a specific approach to thinking—a kind of thinking that occurs both externally on paper and internally in the mind. Since Ahrens views thinking as writing, it's effectively a writing system as well. If you’ve ever been stymied by “writer’s block,” zettelkasten might be your antidote. But be warned: to reap the benefits of the method requires a significant investment in time and effort. Fortunately, Ahrens’ book requires a smaller investment: it’s both short and accessible. There may be more succinct introductions to zettelkasten online, but you’ll be hard pressed to find a more persuasive advocate than Ahrens.

Pros: Ahrens effectively moves between practical and theoretical dimensions of the system. Some might argue that the practical passages are too short and that the book lacks enough concrete examples.

Cons: There are several sections of the book which turn into citation-soup where Ahrens refers to numerous academic studies in rapid succession. The info-overload can be overwhelming.

Verdict: 8/10

Notes & Highlights

Part I: Introduction

Chapter 1: Everything You Need to Know

  • Workflow is an important aspect of writing and note-taking (often overlooked or neglected when it comes to instruction/learning).

  • A useful workflow should facilitate movement between tasks.

  • Having a useful note-taking system relieves you of the burden of needing to hold information and facts in your head. It frees your mind to focus on the synthesis of ideas and the underlying argument.

  • A good system should provide the following:

    • Effective storage of thoughts and ideas.
    • Facilitate connections, discovery and synthesis between different ideas.
    • Ensure that stored ideas are accessible for future use.
    • Ensure that ideas include useful references to 3rd party sources (e.g. bibliographic citations).
    • A simple, repeatable process that ensures a long-term habit is maintained.
  • “When it comes to writing, everything, from research to proofreading, is closely connected. All the little steps must be linked in a way that will enable you to go seamlessly from one task to another, but still be kept separate enough to enable us to flexibly do what needs to be done in any given situation.”

  • Slip-box (aka “zettelkasten” in German): A note-taking system used by 20th century German social theorist Nicholas Luhmann.

    • System involves recording short notes on small pieces of paper, creating references and cross-references to those notes across other notes.
    • Luhman had two slip-boxes: (1) A bibliographical archive and (2) an ideas archive.
    • The bibiliographical archive: Individual note cards held a source citation one one side and a brief note about the contents of the source on the other.
    • The ideas archive: Individual note cards contained a single idea or observation on one side of the card. The note might include cross-references to other 3rd party sources (bibliographic citations) AND references to OTHER individual note cards.
    • The ideas archive would include periodic “index notes” which served as entry-points into a given topic.
  • “More often than not, a new note would directly follow up on another note and would become part of a longer chain of notes…rarely would a note stay in isolation.”

  • Luhmann did not simply copy ideas or quotes verbatim. He would also contextualize the ideas in the notes and connect them to other broad concepts.

  • Luhmann did not organize notes by topic. Instead he used a fixed numbering system to maintain topical “abstraction.”

    • When adding a new note, he would revisit existing notes and update any connections between them and the new note.
    • Modern slip-box users can use digital technology to create keyword tags or hyperlinks between related materials.
  • “Luhmann developed topics bottom up then added another note to his slip-box, on which he would sort a topic by sorting the links of the relevant other notes.”

Chapter 2: Everything You Need to Do

  • Writing is easier when you have all the source materials ready in advance: ideas, arguments, quotes, citations, and references.
  • Zettelkasten helps with writing: You assemble your notes, put them in logical order, turn the notes into draft prose, edit, review and complete your work.
  • “Writing these notes is also not the main work. Thinking is. Reading is. Understanding and coming up with ideas is…the notes are just the tangible outcome.”
  • Writing is, without dispute, the best facilitator for thinking, reading, learning, understanding, and generating ideas we have.
  • “If you want to learn something for the long run, you have to write it down.”
  • “If you want to really understand something, you have to translate it into your own words.”
  • The steps to writing a note:

    1. Make fleeting notes: Short notes that capture an idea in the moment. This type of note does not have to be fully formed, just supply sufficient information so that you can return to the idea at a later time and expand upon it. Capture now, process later.

    2. Make literature notes: Notes about the content you consume (e.g. written content, spoken word, etc.). Like the fleeting note, this should be short so that you can expand on it later. Since these notes are tied to source material, you need to capture bibliographic information (so you can return to the source as necessary).

    3. Make permanent notes: The fleeting or literature note is now added to the slip-box.

      • Review your interim notes regularly (book suggests daily).
      • Consider the contents of the note. Thinking about context, related ideas, relevance to your current research.
      • Ask: Does this new information contradict existing ideas in my slip-box? Confirm? Correct? Clarify?
      • Consider: Does this information combine with other ideas to form something new?
      • Consider: What new questions does this information pose?
      • “Write one note for each idea and write as if you were writing for someone else. Use full sentences, disclose your sources, make references and try to be as precise, clear, and brief as possible.”
      • Interim notes can be discarded after recording the permanent note.
    4. Add permanent note to the slip-box:

      • File your permanent note into your note archive.
      • Add links to other related notes to the new note and vice versa.
      • Update any relevant index notes with the new note (so you can find the new note at a later date).
    5. Develop topics, questions and research: Work within your note system with a bottom-up approach. Use the notes and ideas to construct connections and new insights.

      • Strengthen and bolster current areas of inquiry.
      • Followup on open questions generated by your notes.
      • “Do not brainstorm for a topic. Look into the slip-box instead to see where chains of notes have developed.”
      • “The more you become interested in something, the more you will read and think about it, the more notes you will collect and the more likely it is that you will generate questions from it.”
    6. Select a topic that has been developed: You can now work with topics based on what you have not based on fuzzy ideas or conjecture.

    7. Turn your notes into a rough draft: Translate and expand your notes into coherent prose.

    8. Edit and proofread

  • Ahrens suggests not being overly discriminating or dismissive about what ideas or inspiration to turn into a note: “Gather what you encounter along your way and don’t let any good idea go to waste.”

Chapter 3: Everything You Need to Have

  • Focus on the essentials. Do not overcomplicate things unnecessarily.
  • “Good tools do not add features and more options to what we already have, but help to reduce distractions from the main work, which here is thinking.”
  • A focused brain and a collection of ideas to assist with thinking is all you need. Everything else is clutter.
  • Whether analog (pencil and paper) or digital (note-taking software) the note needs to capture bibliographic or reference information and the note itself.

Chapter 4: A Few Things to Keep in Mind

  • “Tools are only as good as your ability to work with them.”
  • You must put effort and understanding into the tool in order to get the most out of it. In other words: The utility of this note-taking method is only as good as the care you put into learning and working with the system.

Part II: The Four Underlying Principles

Chapter 5: Writing Is the Only Thing That Matters

  • Don’t view studying as preparation for independent research; view studying as independent research.
  • Facts and knowledge should be shared. “An idea kept private is as good as one you never had.”
  • Writing things down is the surest path to sharing knowledge (first with yourself and then with others).
  • The criteria for a sound argument is universal regardless of the source/author: coherent and factual.
  • The presentation and production of knowledge cannot be separated, but are rather two sides of the same coin.”
  • Take a holistic view to learning:

    • Non-holistic view: Sees activities of reading, studying and writing as independent siloed tasks. Engaging in one takes away from the others.
    • Holistic view: Sees the activities as reinforcing parts of a system. Reading is an input into the system. Writing is an output.
  • Being able to summarize, explain or describe an idea in your own words is critical to first understanding it and then taking that idea and turning it into something new.

Chapter 6: Simplicity Is Paramount

  • Simple ideas are powerful.

  • Boxes as an example. Story of Malcolm McLean and the development of the modern shipping container. The core idea is that boxes are a simple, but powerful tool. In the short-run the innovation resulted in strong pushback from ship owners and stevedores. Long-run the innovation resulted in massive logistical efficiencies.

    • Critical fact is that every part of the logistical system had to be changed in order to realize the benefits of the innovation.
    • “When the advantages became obvious, second-order effects came into play and went into a self-reinforcing positive feedback loop.”
  • One lesson of McLean with respect to note-taking: To reap the benefits of the slip-box method requires an overhaul in your workflow and long-term thinking to reap the greatest rewards from the system.

  • Most note-taking systems organize by topic. The slip-box standardizes all notes according to the same format.

  • “Everything is streamlined towards one thing only: insight that can be published.”

  • “The slip-box is designed to present you with ideas you have already forgotten, allowing your brain to focus on thinking instead of remembering.”

  • Three types of notes:

    1. Fleeting notes: Temporary reminders that will be discarded. Some of these fleeting notes may be subsequently recorded as permanent notes.
    2. Permanent notes: Notes that are saved in a slip-box and are forever comprehensible and reusable by the note-taker.
    3. Project notes: Notes relevant to a single project. Can be discarded or archived once a project is completed.
  • Common errors that impede writing output:

    • Confusing the three note categories. Co-mingling notes from all categories obfuscates the meaningful and the meaningless. Maintaining this hierarchy of notes is critical to maintaining the quality of the permanent notes in the slip-box. Discretion must be maintained when considering which ideas are important and deserving of permanence.
    • Collecting notes only for specific projects: Without a permanent archive of ideas, each project is treated independently and must be started “from scratch.”
  • “The more you learn and collect, the more beneficial your notes should become, the more ideas can mingle and give birth to new ones—and the easier it should be to write an intelligent text with less effort.”

  • Fleeting notes should be reviewed as soon as possible (while the meaning, significance and context are still remembered).

  • Permanent notes should be recorded so that the significance and context of the idea are preserved for future reference.

  • “A good indication that a note has been left unprocessed too long is when you no longer understand what you meant or it appears banal.”

  • Project notes include: Manuscript comments, project-related literature, outlines, draft snippets, reminders, to-do lists and the draft itself.

Chapter 7: Nobody Ever Starts from Scratch

  • They way we are taught to write in school and our mental model of the act of writing are fundamentally flawed.
  • A common (flawed) linear approach to writing:

    • Select a topic
    • Research the topic
    • Write about the topic
  • Ahrens argues that the linear approach is nonsensical. A good question is the result of having already carefully considered a topic a priori.
  • “Every intellectual endeavor starts from an already existing preconception, which then can be transformed during further inquiries and can serve as a starting point for following endeavors.”
  • “We will not be guided by a blindly made-up plan picked up from our unreliable brains, but by our interest, curiosity and intuition, which is formed and informed by the actual work of reading, thinking, discussing, writing and developing ideas…”
  • Questions and topics are the natural (and unforced) emergent byproducts of intellectual curiosity, reading and learning.
  • Instead of brainstorming (which relies on only the immediate ideas available in your head and which can be drawn upon in the moment), Ahrens argues that your slip-box is a better solution for idea generation.
  • “Having trouble finding the right topic is a symptom of the wrong attempt to rely heavily on the limitations of the brain.”
  • “If you develop your thinking in writing, open questions will become clearly visible and give you an abundance of possible topics to elaborate further in writing.”
  • More importantly: using the slip-box method helps you write about the topics and questions that are interesting to you (which will increase the probability of completing your written project).

Chapter 8: Let the Work Carry You Forward

  • “A good workflow can easily turn into a virtuous circle, where the positive experience motivates us to take on the next task with ease…but if we constantly feel stuck in our work, we will become demotivated and much more likely to procrastinate…”
  • Feedback loops are critical for learning progress and motivation.
  • Immediate feedback loops are ideal (preferable to monthly or annual feedback loops).
  • There are even internal feedback loops we can benefit from. For instance: when you read an interesting idea, see if you can articulate the idea in your own words. The utility and clarity of your prose is a strong indicator of the quality of your comprehension.
  • “The ability to express understanding in one’s own words is a fundamental competency for everyone who writes…the better we become, the easier and quicker we can make notes.”
  • “Expressing our own thoughts in writing makes us realize if we really thought them through.”

Part III: The Six Steps to Successful Writing

Chapter 9: Separate and Interlocking Tasks

  • Give each task your undivided attention.

  • Multitasking is not a good idea.

    • People who multitask feel more productive.
    • Research studies conclude that multitasker performance does not match single-taskers in output.
  • The activity we call “writing” is actually a bundle of separate but related activities and skills: reading, understanding, reflecting, idea generation, making connections, structuring, organizing, editing, correcting, rewriting.

  • Different types of tasks require different types of attention.

    • For example: Ahrens recommends using a printout for the task of proofreading rather than proofreading directly onscreen. The reason is that if you attend to the task onscreen, you might be tempted to also engage in the act of editing and rewriting.
    • Create mental and physical distance between different tasks. For instance when we reread our text as a critic (looking for holes) we must divorce our mind from the author (who is overly familiar with the text).
    • The tasks of writing are iterative and can be revisited throughout the writing process.
  • What you mean is not the same as what you have written. In other words: what you have written may or may not contain what you intended. You, the writer, continuously work to ensure that your meaning is contained in your writing for the outside observer.

  • Become an expert instead of a planner:

    • “It is a matter of practice to become good at generating insight and write good texts by choosing and moving flexibly between the most important and promising tasks, judged by nothing else than the circumstances of the given situation.”
    • “To be able to become an expert, we need the freedom to make our own decisions and all the necessary mistakes that help us learn.”
    • “Experts…have internalized the necessary knowledge so they don’t have to actively remember rules or think consciously about their choices.”
    • This idea is really about action. Planning is thinking about the thing. Ahrens urges people to just do the thing. Expertise arrives through doing.
  • Don’t waste limited short-term mental memory with thoughts that can be delegated to an external system.

  • Zeigarnik effect: Open tasks occupy our short-term memory. Give those tasks closure either by completing them or by writing them down.

  • Reduce the number of decisions that need to be made.

    • A routine can help.
    • A “reliable and standardized working environment is less taxing on our attention…”

Chapter 10: Read for Understanding

  • Read with a pen in hand.
  • Remember that copying quotes without original context changes the meaning of a quote.
  • Handwritten notes are most effective for recall and summarization.
  • Top-down approach to writing (i.e. starting from a presupposed hypothesis) is especially susceptible to confirmation bias.
  • Combat confirmation bias by seeking, recording and making notes about counter-arguments to your ideas. This will, in turn, strengthen your ideas.
  • Learn to extract the “gist” from a text. This can be a short, even single sentence, written summary. This can be on a micro or macro level (e.g. the gist of a paragraph or the gist of an entire book).
  • Practice writing short summaries to find the optimal way to express an idea. Aim for simple, not simplistic.
  • Don’t mistake familiarity for understanding. Be cognizant of the mere-exposure effect (where personal preferences are generated by exposure to something rather than for any underlying objective reason).
  • Elaboration is a powerful learning tool. Elaboration is the act of taking an idea. Understanding its original context and then exploring its meaning and context in other ways. For instance, consider how the idea could be combined with other threads of inquiry. Consider followup questions to pursue.
  • Slip-boxes are powerful tools for elaboration.

Chapter 11: Take Smart Notes

  • Information must be understood within its context but it must also be considered beyond its context.
  • Thinking is not an exclusively internal process.
  • Thinking requires a combination of internal and external thinking.
  • Writing is not the byproduct of completed mental activity. It is a core part fo the activity.
  • Richard Feynman on his thinking process when a historian looked at Feynman’s notebooks: “No, no. They aren’t a record of my thinking process. They are my thinking process. I actually did the work on paper…you have to work on paper…”
  • Consider two different characteristics of human memory: storage strength and retrieval strength.

    • We tend to focus on storage strength (i.e. memorization of facts).
    • Retrieval strength is accessing stored ideas. Building connections between ideas improves informational utility and ease of retrieval.

Chapter 12: Develop Ideas

  • “Notes are only as valuable as the note and reference networks they are embedded in.”
  • Remember that the slip-box is not a replacement for Wikipedia. Comprehensiveness is not the goal. The goal is to generate insights for the ideas and topics of interest to you.
  • Digital slip-boxes can use keywords to link notes thematically. Keywords can be generated with one of two purposes in mind:

    • Storage-first keywords (archivist): Which keyword is the most fitting?
    • Retrieval-first keywords (writer): In which circumstance will I stumble upon this note?
  • “Keywords should always be assigned with an eye towards the topics you are working on or interested in, never by looking at the note in isolation.”

  • Keywords are a critical part of the thinking process. Do not shortchange this task as it facilitates connections between notes.

  • Two types of cross-references for digital slip-boxes:

    • Index or entry-point notes: These are high-level notes for a given topic that are the starting point for a deeper branching of related notes.
    • Note-to-note links: These references highlight lateral connections between individual notes.
  • When you find an idea that already exists in your slip-box but is slightly different, this is an opportunity to add a new note detailing the nuance or variation. These similar but different ideas are important and are easily overlooked without a system like a slip-box.
  • Comparing notes and detecting contradictions, paradoxes and opposition are important facilitators for insight.
  • Feature-positive effect: Phenomenon in which we overweight information that is readily or most recently available to us (similar to recency or availability bias).
  • “We learn something not only when we connect it to prior knowledge and try to understand its broader implications (elaboration), but also when we try to retrieve it at different times (spacing) in different contexts (variation), ideally with the help of chance (contextual interference) and with a deliberate effort (retrieval).”
  • Steve Jobs (businessman): “Creativity is just connecting things. When you ask creative people how they did something, they feel a little guilty because they didn’t really do it, they just saw something.”
  • Practice asking counter-factual questions like “what if?”

Chapter 13: Share Your Insight

  • User your slip-box to identify clusters of ideas that interest you. This is the raw material and inspiration for more developed writing.
  • Slip-box encourages a bottom-up approach to idea generation.
  • “Good questions are in the sweet spot of being relevant and interesting, not too easy to answer but possible to tackle with material that is available or at least within our reach.”
  • Keep the structure of your linear writing flexible. The slip-box will facilitate this since individual notes comprising the base materials of your writing are highly modular atomic pieces of information that can be swapped, developed and reordered as needed.
  • ‘Be generally skeptical about planning, especially if it is merely focused on the outcome, not on the actual work and the steps required to achieve a goal.”

Chapter 14: Make It a Habit

  • “Get into the habit of fetching pen and paper whenever we read something…if we manage to establish a routine…it becomes much easier to develop the urge to turn these findings into permanent notes and connect them with other notes in the slip-box.”

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