I have an attention deficit disorder, and I struggle with forming and sustaining elaborate thoughts and ideas. This is especially the case in the realm of intellectual productivity. My ADHD doesn’t allow me to properly externalize my thoughts, and I frequently find myself in shallow cyclical thinking whose only purpose, it seems to me, is to further exaggerate my symptoms, overwhelm my executive functions, and fatigue my mind. Flimsy thoughts, distractions, and hyperactivity have been my nemeses ever since I started to consciously address my symptoms. An area of recurring pain and disorientation has been knowledge management. I consider myself a generalist (perhaps a side-effect of my wandering mind), yet I have never been able to sustain a robust system for managing my writing, research, and notes. Everything that I have tried has fallen apart at some point in the process.
Three years ago, however, I adopted a knowledge management system that productively utilizes my ADHD tendencies in pursuit of knowledge and clarity, and it hasn’t failed me yet. The system respects the generalist attitude that I have adopted and has transformed the way I form ideas and consume information. Its name is Zettelkasten and its creator is the famous German sociologist Niklas Luhmann.
A Zettelkasten consists of individual notes where each one represents an idea, categorized in a hierarchical, alphanumeric manner, which allows the author to infinitely branch out notes, hyperlink them, and accumulate them in “hub” notes to generate lines of thought, topics and research areas.
In this article, I will briefly describe how the method works, how it has helped me in my intellectual endeavors, and point you to helpful resources for getting started. Having said that, this article, although quite long, is not a comprehensive representation of the Zettelkasten method. Its goal is only that of a superficial introduction as a potential tool for non-fiction writers, researchers, life-long learners, and, of course, ADHD “generalists.” The discourse on the method is much more involved, and I have linked several sources below that better articulate it.
With a little bit of patience and a few (perhaps a lot of) false starts, you too can forgo the conventional folder structures and tagging systems that plague the knowledge management world for a serendipitous, hyperlinked conversation partner, your own Zettelkasten.
All you need to get started is pen and paper (for an analog system) or plain text files on your computer.
Niklas Luhmann and his Zettelkasten
Luhmann, 1927-1998, was a professor of sociology at Bielefeld university in Germany, and was one of the last advocates of a “grand theory.” To pursue this endeavor he followed developments in disciplines outside of sociology such as law, theology, biology, public administration, political science, etc. By the time he died, he had published more than 500 works and had left many more unfinished, which were subsequently published after his death.
As an avid reader and note-taker, he considered his notes as assets to his intellectual future, and so he never discarded any of them, in expectation that they would aid him to the development of new ideas later on. He found conventional knowledge management to be flawed and a hindrance to serendipity. With trial and error, he devised his own system that was topic-agnostic and had the ability to surprise him with long-forgotten ideas and new insights. Its power was such that he referred to it as “a second memory.” The system consisted of slips of paper or index cards (his zettels) arranged in a wooden box drawer (a kasten)—thus the name Zettelkasten—one after the other, wherein each note bore a unique number on the upper left corner so that he could individually address and locate his ideas as they dispersed themselves across the file.
In addition to identification and atomic reference, the numbered sequence of cards allowed him to infinitely expand and interconnect his line of thoughts, thus enabling him to merge otherwise distinct concepts and patterns of thinking that, under conventional knowledge management systems, would require separate filing locations and more rigid structures.
In absolute terms, Luhmann’s file consisted of 90,000 notes, divided in two collections. The first collection (1951-1962) included topics in law, public administration, political science, philosophy, sociology, and other areas. The topics were spread in 23,000 cards divided over 108 sections, in addition to a keyword index and two bibliographies. The second collection (1963-1997) included just 11 top-level sections and hundreds of subsections, totaling 67,000 notes. The fact that the second collection only employed 11 top-level sections, or topics of inquiry, demonstrates a problem-solving approach whose focus was to make cross-topic connections and not rigid categorization (Schmidt, 2016). It is the second collection’s functionality and promise as a system that enables serendipity that has thrust Luhmann into the spotlight in the recent years.
To the outsider, Luhmann’s system resembled a chaotic accumulation of notes irrespective of topic and subject, though in reality the system was depended on a complex interconnected structure, which promoted a systematic concentration of topics and their evolution, and which did not strictly adhere to a traditional filing method. Notes relating to each other were placed in physical proximity in accordance to his numbering system, but before that could happen they had to be assigned a top-level order. Top-level ordering (as indicated by the first number in a card; e.g., “.0 = Ancient civilizations”) was important in the beginning but later became largely a matter of ambiguity because over time, notes accumulated in large clusters and branched away from the top-level relationship, transforming into their own topics and lines of thought that bore minimal resemblance to the original category. Therefore, top-level order was quickly rendered redundant and the placement of notes was solely determined by their relationship to existing ideas in the file.
Referencing & the keyword index
According to Schmidt, J. (2016), Luhmann believed that the usefulness of a new note in the file was determined based on the ability to relate it to existing ideas. This method of filing created a problem because it was entirely conceivable to have more than one suitable place for a note. This is where internal referencing and a keyword index were utilized to solve the problem.
When similar notes were found in other parts of the file, a referencing system was deployed to bring everything together, thereby further obscuring the initial categorization from the reality that existed in the center of the file. Luhmann used three types of references to connect his ideas:
An outline structure of ideas that needed to be addressed in a section, placed at the the very beginning of a cluster of notes.
Collective references (or hub notes): At the beginning of sections, he included notes from other parts of the card index that might relate to the topic being developed.
Single references, which resembled hyperlinks, directly referencing individual notes in the file.
Finally, the chaos of references and endless lines of thought was tamed by utilizing a central keyword index. The keyword did not aim to capture the entirety of the file, for it was not conceived of as a table of contents. Its main goal was to provide entry points to notes in the file so that ideas and topics could be located more efficiently. The index also aimed to accomplish thematic completeness (Schmidt, 2016). Keywords where chosen wisely and sparingly. Luhmann determined that they should be purposefully broad and contextual so that a search for a specific line of thought would uncover other potential referenced paths and clusters of ideas that he could take advantage of, and which could provide fresh insights and inquiries.
My implementation & the anatomy of a note
Now that I have explained a little about how Luhmann’s method works, I want to show you my digital implementation of the method which utilizes markdown files (plain text) and two folders: one bibliographical and another for the zettels. The bibliographical section, unlike my zettels, is alphabetized and contains literature notes from my readings. It acts as a simple reference archive.
The following list of notes has been copied from a larger section of my zettels folder. The number six, before the dot, denotes “psychology” in my index, which is a top-level section, but entries relating to this category can be found all across my file. For example, I maintain a section that tackles stories, fiction, and narratives wherein psychological concepts and ideas tend to develop. When that happens, I either hyperlink notes so that I can establish a bidirectional relationship between them or input them in the reference hub note in my psychology section (usually that would be the very first note; e.g., 6.0 – Psychology Reference).
As you can see, the list is represented alphanumerically. Let’s focus on 6.2h. When I created the note 6.2h, I kept reading and researching and eventually wrote another note which I marked as 6.2i. Further reading uncovered additional ideas that were more related to 6.2h than to 6.2i or any other note, and so I alternated from letters to numbers to be able to input my new notes directly below 6.2h. This is how clusters are created. These ideas do not need to be hyperlinked to each other because they are placed in close proximity and so a search for one note will uncover its surrounding notes as well.
Now let’s examine the anatomy of a single note:
Every note that I create is marked with an alphanumerical ID, followed by a short description of the contents of the note, which comprises the title of the file, helping me identify it when I perform searches. Below the title I place the hyperlinks. This note is found in a cluster in the psychology section, but I have referenced 21.2f (an idea that resides in a different part of the file) as a note that directly relates to it. If I click on the hyperlink, I will be transported to the notes within 21.0 which contains new branches of ideas and topics for exploration.
Below the direct references I enter the contents of the note. I aspire to make my notes as short as possible so that one note holds a single idea.
The last and most important tool in my system is a manual index that provides me with entry points to my ideas and research. As I mentioned before, the goal of the index is not to capture every note in the file but to display thematic completeness, to act as an entry point only. Luhmann’s index was alphabetized, but I have chosen to group my entry points in relation to each other since I do not yet have a large enough number of zettels to necessitate an alphabetized order for clarity’s sake.
Why it is a great system for the ADHD mind—and everyone else
Friends often ask me why this knowledge management method is a good fit for my ADHD mind. I have come up with a few reasons through observations and reflection.
First of all, you don’t have to worry about rigid organization: you can link your clusters to other locations or hyperlink individual notes. You can pull together disparate ideas in “hub” notes to create new topics. You maintain an index that is not permanent and can change at anytime to reflect the thematic evolution of your ideas. You can work on a number of interlinked projects simultaneously. The system is designed to allow you to work on what you are interested the most: If you lose interest on a project or line of thought, let it be and you might stumble upon it as you explore and link different ideas later in the process. Zettels or notes are designed to be atomized, individual thoughts or ideas, not paragraphs, thus making it easier for you to construct and visualize logical sequences and arguments. It encourages you to think in writing, thus externalizing your ideas into words, revealing their true meaning: that way, scattered thinking can be clarified and adjusted in the broader context of your interests. You do not lose your notes, for they have a permanent location. The index is your treasure, providing you with entry points to your thinking and sources. No space limitations: you can infinitely expand your writing in any direction and link ideas as densely or sparingly as you want.
Personal benefits from using the method
Sönke Ahrens, the author of How to Take Smart Notes, one of the best introductions to the Zettelkasten method, states that every intellectual endeavor begins with a note. Conventional wisdom follows that one should first identify a topic and then begin researching it. The Zettelkasten approach, however, encourages you to look inside your notes and identify clusters that you can expand upon to form a manuscript. And this is exactly what I did in my senior year of college: I utilized the bottom up approach of analysis and idea generation that my Zettelkasten afforded me, and I produced papers that earned me the marks representative of my note-taking effort. That was in contrast to my fellow classmates, who would take days or even weeks working on their papers, hunting for evidence to satisfy their topics, in a trickle down approach. By the end of my senior year, my Zettelkasten had reached a critical mass of notes where new ideas simply joined existing ones like Legos.
My capstone project (the culminating project of a class in college) was a broad, policy-orientated essay where every student could pick their own topic. I knew where my interests laid, because I was clustering them and linking them across my Zettelkasten for months and so unlike my peers, I did not have to brainstorm a research question and then go hunting for the evidence: I possessed the evidence and critical opinions, and the only thing I had to do was piece them together. Of course, this process did not help me with all my projects, for I only take notes on the things that I find intellectually rewarding and interesting. At times, I was forced to use the traditional trickle down approach to write papers, but over the course of months that approach had become less essential to my workflow.
Outside of academics, I use my Zettelkasten to develop ideas, arguments, and views that I can later use in essays, books, and articles. (This article was written by compiling existing ideas in my Zettelkasten.)
Alphanumerical IDs, timestamps, and links
In the modern Zettelkasten world, new software tools bring emphasis on timestamps as unique IDs—e.g., 210622163204 (Year/Month/Day/Time), which can be automatically generated and used to identify a specific note—but it is my belief that if you really want to bring about the full scope of the method, as constructed and realized by Luhmann, you have no choice but to use a hierarchical numbering system that alternates letters and numbers (or something thereof). I understand that there are variations of the method (for example, using it as a relational database, embracing computer search, tags, and hyperlinking), but despite the number of different adaptations that exist, Luhmann’s alphanumerical order triumphs as the most logical and sustainable. It should be conceded, however, that, compared to newly refined digital approaches, Luhmann’s technique provides a little bit more friction, in terms of placing zettels in their respective positions, but it overall better facilitates the identification of notes and visualization of clusters because hierarchy physically concentrates ideas, allowing for less, yet equally effective linking by applying links only to distanced areas of the file. Many new approaches on the internet lack that natural concentration of notes thus forcing excessive linking, which tends to become unsustainable as one’s file grows.
Furthermore, the alphanumerical structure itself can assist one’s thinking. Even though its impossible to remember everything written within the notes themselves, the fact that they are placed in a sequential order and are branching out allows you to have a mental outline of the topics and ideas within your file, thus giving you an extra degree of independence by being able to communicate your ideas without the presence of the notes.
A feasible alternative to the alphanumerical method that I have thought of is branching zettels in a outline form so that I can have a permanent location, link across them, and indent to denote lines of thought, yet this also proves insufficient if I want to expand too deeply, for too much indentation visually impends the structure that I seek to establish. Indentation becomes much more subtle in a numbered sequence.
Friction in your Zettelkasten
To expand a little bit more on the idea of friction, a frequent justification for using software implementations is to have the ability to remove it or minimize it. Friction, however, is an important part of a successful Zettelkasten, that’s why I attempted to replicate Luhmann’s system using plain text files and a single folder as my tools to keep my system more intentional. The same methodology but on a screen. Obviously, all processes become faster than using paper, yet slow enough to cause the author to carefully consider aspects such as branching, hierarchy, keyword index maintenance, and cross-file referencing (achieved either through direct links or hub notes). For instance, if I need to create a new note, I have to consider its position based on its relationship with existing ideas and then assign it a unique ID (e.g., 3.6a – Niklas Luhmann) which must then be linked to other related notes and topics (though this is not always the case because some ideas are specifically contained in clusters) as well as be reachable from the index. It might seem tedious and slow, but then again, Luhmann did all of that using nothing but a pen and paper.
Lastly, one of the main characteristics of a successful Zettelkasten implementation is the system’s attractive force towards the author. The system should motivate you to tinker with it, explore it, endlessly write in it—as a means of thinking—and pursue a journey of interconnected thought patterns and ideas. In other words, it needs to be addictive, to actively be calling for your attention, to be a externalized, polished reflection of your mind and intellectual endeavors. Then, and only then, you will get the most out of it.
There is nothing worse than an idle system, for that would not be a Zettelkasten but an archive.
Sources and reading
There is a lot of discussion about the Zettelkasten method on the internet. Below you will find a list of sources for further reading, as well as a few software tools that I recommend.
How to Take Smart Notes – This was my first introduction to the Zettelkasten method. It is a practical guide as well as a thesaurus of research on learning, mastery, and note-taking.
zettelkasten.de – Articles and forums dedicated to the Zettelkasten method.
Johannes F.K. Schmidt (article 1) & (article 2) – Schmidt provides the most detailed account of the innerworkings of Luhmann’s Zettelkasten. Some paragraphs tend to be a little dense, so you might have to re-read some sections.
Luhmann’s digitized Zettelkasten – Follow this link to get lost in the oasis of Luhmann’s zettels.
Ahrens, S. (2017). How to take smart notes: One simple technique to boost writing, learning and thinking: for students, academics and nonfiction book writers. CreateSpace.
Schmidt, J. (2016). Niklas Luhmann’s Card Index: Thinking Tool, Communication Partner, Publication Machine. In A. Cevolini (Ed.), Library of the written word: Vol. 53. Forgetting machines. Knowledge Management Evolution in Early Modern Europe (1st edition, pp. 289-311). Leiden: Brill.
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