Zettelkasten — How One German Scholar Was So Freakishly Productive

ByDavid B. Clear

Luhmann wrote over 70 books and more than 400 scholarly articles using the Zettelkasten notetaking method

(Versión en español aquí)
(Deutsche Übersetzung hier)


Luhmann was extremely prolific.

During his almost 40 years of research, he published more than 70 books and over 400 scholarly articles on a wide variety of subjects, connecting sociology with such diverse topics as biology, mathematics, cybernetics, and computer science. That’s more than seven books every four years for his whole career — in addition to a boatload of articles. And those books are no hastily thrown together nonsense. They are classics that made him one of the most important sociologists of the twentieth century (pdf).

His productivity is even more impressive considering how old school he was. Shortly before his death, in a radio interview with Wolfgang Hagen, he revealed that he used no computers, only pen and paper and a typewriter, which he operated using hunt and peck typing.

When asked how he published so much, Luhmann used to answer “I’m not thinking everything on my own. Much of it happens in my Zettelkasten. My productivity is largely explained by the Zettelkasten method” (original in German).

Because of statements like these, Luhmann’s Zettelkasten acquired a mythical status and has been deemed so valuable that it’s currently the subject of its own research project. But Luhmann never made a secret out of his method and it’s actually fairly simple to understand. And that’s good news! It means we can adopt his method and get the same benefits that made him such an eminent intellectual:

  • learn better,
  • think better,
  • publish more, and
  • be more creative.

So if you’re writing nonfiction or are a knowledge worker of any kind, you should know about the Zettelkasten notetaking method.

What is a Zettelkasten?

Luhmann described his Zettelkasten in different ways. Sometimes he called it a conversation partner and sometimes he described it as a second memory, cybernetic system, a ruminant, or septic tank.

A ruminant? A septic tank? What on Earth is he talking about?

Let’s begin with the word “Zettelkasten”. This Teutonic word can be broken down into two components: “Zettel”, which means note or slip of paper, and “Kasten”, which means box. A Zettelkasten is therefore nothing more than a box of notes, properly called a slip box or card index in English.

Luhmann’s Zettelkasten was in fact a piece of furniture. It comprised six stacks of four wooden drawers each, with each drawer filled to the brim with paper notes. This is how it looked:

A bit anticlimactic, isn’t it?

A piece of furniture? That’s what made him so productive?

Well, not exactly. It’s like me handing a pencil to a Neanderthal and the Neanderthal asking “That’s it? This little stick is what allows you to communicate through space and time with other human beings and remember things forever?”

As you’ll see, the Zettelkasten method is as much about a piece of furniture as writing is about a little stick. But before we get to Luhmann’s method, let’s first review the drawbacks of some other notetaking systems.

Why other notetaking systems fall short

If you’re anything like me, you’ve tried taking notes in all sorts of ways.

  • You’ve written in paper notebooks,
  • you’ve written on the margins of books and printouts,
  • you’ve used smartphone and web apps,
  • you’ve taken notes using a word processor or text editor and tried to organize the resulting files in a sensible folder structure on your computer,
  • you’ve drawn both analog and digital mind maps and concept maps,
  • you’ve used outliners, and
  • you’ve buried your desk under a chaos of post-it notes and random slips of paper.

The problem with all these approaches is that they don’t really help you find connections among ideas. Instead, they lock ideas away to be forgotten in a box under your bed, in the cloud, or in a folder somewhere on your computer.

Imagine you’ve read a popular science book three years ago, a book about personal finance one year ago, and now you just read a blog post about how to be more productive. Each of these sources has ideas and these ideas might be connected in some way. Moreover, six months ago you might have had some clever idea of your own that might be related as well. Yet, you’re unable to see any connections among these ideas. Why? Probably because you didn’t take any notes. But even if you had, you’d still be unable to see any connections.

If you wrote notes into paper notebooks, you’ve fixed them into a rigid chronological order. The ideas are stuck to the pages as if you had poured concrete over them. If there is a connection between an idea at the bottom of page 17 and an idea at the top of page 89, you’re not going to see that connection. You’ve got the same problem if you wrote your notes in the margins of books and printouts.

The usual digital notetaking approaches don’t fare any better. Tools like Evernote quickly devolve into dumping grounds as you succumb to the collector’s fallacy — the tendency to collect heaps of information without ever doing anything useful with it. If instead you keep your notes in files and folders on your computer, they’ll also soon end up forgotten and collecting digital dust. And even if you don’t forget your notes, they are still not organized in a way that lets you easily see connections between ideas.

If we now consider mind maps, concept maps, and outlines, we’re getting closer to a solution. These tools are a good approach to find relations among ideas. The problem, however, is that they only allow you to properly work with a few dozen ideas. You’re certainly not going to put 90,000 ideas into a single concept map over the time span of 40 years and draw connections among the ideas. But that’s precisely what Luhmann did with his Zettelkasten!

What made Luhmann’s approach unique?

Had Luhmann kept his notes in notebooks, they would have looked like this:

The notes would have been cast into a rigid structure where it’s impossible to rearrange them.

If, on the other hand, he had simply kept them on index cards or slips of paper, without any organization, they would have looked like this:

The notes would have been free-floating, but it would have been impossible to track how they relate to each other.

He could have done what other users of slip boxes did at the time and kept his notes on index cards and then filed them away by category into separate drawers or folders. The result would have looked like this:

This provides some organization and looks tidy.

The problem with this approach, however, is that each folder constitutes a separate silo even though real-world ideas rarely fit into neat categories. For instance, the idea of complexity is present in biology, physics, mathematics, society, technology, and who knows where else. So in which folder should you keep a note about the concept of complexity?

A second problem is that a folder-based approach makes it hard to draw connections between ideas that have been filed away in different folders. Each note is clearly related to the ones in the same folder, but a note may also be related to notes in different folders. For instance, a note in Folder 1 might also contain ideas that are connected to some of the notes in Folder 2 and Folder 3. With a folder structure you can’t capture these relationships.

This brings us to the next approach, which consists in using tags instead of folders:

This is a big improvement over folders because now the categories are no longer mutually exclusive. A note can have more than one tag and you can look at your whole collection from different points of view, depending on which tag you’re focusing on.

Tags are commonplace now and many notetaking apps support them. But you don’t need a fancy app to use them. Luhmann knew about them and in fact used them in his paper-based Zettelkasten.

Despite the advantages of tags, Luhmann wasn’t happy with tags alone. He still found them too limiting.

As anyone can attest who has filed away thousands of notes and dutifully tagged them, tags still make it difficult to see how notes are connected. In fact, with thousands of notes per tag, your collection of notes is just as confusing as if you had no organization at all. Each tag just yields a big messy pile.

Luhmann thus went one step further. Instead of relying on tags alone, he also linked his notes together. The result looks like this:

Notes, and therefore ideas, are no longer just grouped together, but their connections are explicitly tracked. This creates a web of ideas and results in massive advantages.

Think of it this way. The Internet — or the World Wide Web to be precise — is also a web of ideas. When you click on a link, like this one, you’re transported from this page (the one you’re reading right now) to the home page of Wikipedia. From there you can click on further links and in this way move from one webpage to another, thereby exploring the Web.

Now imagine that instead of the Web being a web, all of the world’s webpages had just been dumped into a big folder without any links. All Wikipedia pages, all blog posts, all Medium stories, all the web articles of different newspapers, all YouTube videos, all the gazillion webpages that make up the Web, all just piled onto one big heap inside a folder. You’d never make any sense of it.

Now imagine further that someone proposed that the solution to this mess was to use tags. You’d consider the idea ludicrous. What? I should organize the gazillion webpages in this folder by using what? A million tags? That’s absurd!

No, the way to organize a massive amount of information and make sense of it is to use a web. That’s why the world’s webpages, as well as the neurons in your brain, are organized as a web. And that’s why you should organize all the interesting ideas you want to keep track of over your lifetime as a web of notes as well.

The Zettelkasten’s massive advantage

By using the Zettelkasten method, your notes become entities that are knitted into a larger web of ideas. Instead of the system deteriorating the more you add to it, it becomes better. Again, it’s like your brain. No one would suggest that having more neurons would make you dumber. It’s the same with the Zettelkasten. More notes means more ideas and more connections, and the more ideas and connections you have, the “smarter” your Zettelkasten becomes and the more insightful your writing will be.

Saying that the Zettelkasten becomes smarter is not just poetic language. Luhmann meant that quite literally.

Let me explain.

Claude Shannon, the father of information theory, studied communication and needed some measure for the amount of information that is exchanged when two entities communicate. The measure he came up with is called surprisal (also known as information content, Shannon information, or self-information). Shannon realized that how much information is contained in a message is determined by how surprising the message is.

Wait, what? More surprising means more information? That’s exactly right.

Imagine you ask a duck a question and it answers “quack”. You then ask the duck another question, and it answers “quack” again. You ask it questions over and over, and that silly duck just keeps answering “quack”. You’d quickly realize that you’re not communicating. There’s no surprise ever. The duck is not conveying any information. It’s just saying “quack”. It just isn’t a smart conversation partner.

Now compare that to a mature Zettelkasten, which contains thousands and thousands of ideas. You have a question and with that question in mind you dive into your Zettelkasten, moving from one idea to another by following links among notes. Since it contains so many ideas, which you’ve been collecting over a time span of years, you’ve forgotten a huge chunk of them. The Zettelkasten is bursting with ideas that you added years ago and no longer remember. Thus, if you explore it with a question in mind, the Zettelkasten will provide answers in surprising ways. In this sense, the Zettelkasten is smarter than a duck and it’s why Luhmann described it as a conversation partner.

Of course, to reap these benefits, the Zettelkasten must have reached a certain level of maturity. At the beginning it will just contain a few notes which you won’t find that surprising since you just added them recently. Over time, however, your Zettelkasten will grow from an apprentice to a full-fledged writing collaborator. Meanwhile, it will be at least as good a repository for your notes as a notebook or some fancy app. In fact, a Zettelkasten will probably already be a better notetaking system from the first day as the method has some further advantages.

You’ll learn better

Reading doesn’t magically increase your knowledge. Just because some text has entered your eyeballs and visited your short-term memory, that doesn’t mean you’ve learned from it. In fact, if all you’re doing is reading — and you’re doing so for any purpose other than entertainment — then you’re wasting your time. What has only entered your short-term memory will eventually be forgotten and is useless in the long term. Years later, it’ll be as if you had never read that book or that article.

So if you’re reading to increase your knowledge, take notes. And if you’re going to take notes, use a Zettelkasten.

A Zettelkasten will not only be a safe repository for the knowledge you accumulate over time, but, by forcing you to create notes and then links between those notes, a Zettelkasten will improve your understanding of the reading material. As researchers Annie Piolat, Thierry Olive, and Ronald T. Kellogg put it (pdf):

[Lots of] studies suggest that nearly all non-linear note-taking strategies (e.g. with an outline or a matrix framework) benefit learning outcomes more than does the linear recording of information, with graphs and concept maps especially fostering the selection and organization of information. As a consequence, the remembering of information is most effective with non-linear strategies.

You get that? The linear recording of information, as in a notebook, sucks. Non-linear notetaking, and especially graphs and concept maps, rock. And what is a Zettelkasten if not one massive graph or concept map?

You’ll focus better

This one is from personal experience. I noticed that using the Zettelkasten method allows me to concentrate much better while reading. I think this is because the method turns reading into a mission. I’m not just reading. I’m on a quest to hunt down ideas, extract them from texts, and feed them to my Zettelkasten as notes. I have a crystal clear goal: feed my Zettelkasten. I’m not just reading with some vague intention of becoming smarter. Having a clear goal makes reading much more fun and I always seem to quickly end up in a flow state.

You’ll be less frustrated

The Zettelkasten method makes reading complicated texts less frustrating. You’re not necessarily trying to understand the whole text. You’re just hunting down ideas to incorporate into your Zettelkasten. Who cares if you don’t understand everything? As long as you’re extracting some ideas, you’re growing your knowledge base and the text is being useful to you.

You’ll waste less time

With the Zettelkasten method, research is never a waste of time. You never have to worry about deciding whether some piece of information is worth storing in your Zettelkasten. If it’s interesting, add it, even if you’re unsure if it’ll be relevant to your current writing project.

Remember, a Zettelkasten is intended to store knowledge for the rest of your life. If some piece of information ends up not being relevant now, it may turn out to be relevant eventually. You’re never wasting time by adding more ideas and connections. A Zettelkasten just keeps getting better the more ideas it contains.

You’ll think better

As Don Norman put it in his book Things that make us smart: Defending human attributes in the age of the machine, “The power of the unaided mind is highly overrated. Without external aids, memory, thought, and reasoning are all constrained. […] The real powers come from devising external aids that enhance cognitive abilities.”

Luhmann, with his Zettelkasten method, seems to have stumbled upon just such an external aid. Not only did his Zettelkasten aid his memory by serving as a collection of ideas he could refer back to, but it also improved his thinking. That’s why he said “Without the [Zettelkasten] notes, that is, by only thinking, I wouldn’t come up with such ideas. Of course my head is necessary to write down the insights, but it can’t take all the credit” (original in German).

I think the Zettelkasten’s power as a thinking aid is explained by three main factors.

First, using the Zettelkasten method forces you to write. In particular, according to the method you have to write notes using your own words to ensure that you’ll understand them in the future. And as anyone who’s done any writing knows, writing things down forces you to turn vague notions into clearer thoughts.

Second, whenever you add a new note, the Zettelkasten method forces you to look for already existing notes you can link to. That broadens your thinking by forcing you to consider how new ideas relate to others you’ve encountered before.

Third, a Zettelkasten can store a train of thought. A train of thought is nothing but a sequence of ideas and a Zettelkasten is all about linking ideas. Thus, you can have a train of thought today, store it in your Zettelkasten as a sequence of interlinked notes, and then, anytime in the future, you can continue that train of thought by adding new notes and linking them to the previous ones.

You’ll be more productive

The Zettelkasten method gives you a systematic way to research information, structure your knowledge, and develop your thinking. It gives you a process to follow that ultimately ends up generating new ideas. This has two advantages.

First, having a process to follow automates how to proceed at a given task, eliminating the need to think too much about what to do next. This makes you more efficient and thus more productive.

Second, the number of new ideas is one of the most important measures of productivity for any nonfiction writer. By being a systematic way of generating new ideas, the Zettelkasten method directly affects the output that matters: the number of new ideas to write about.

You’ll be more creative

A Zettelkasten is designed to find connections between any past idea you’ve recorded and any present or future ideas you’ll record. This makes a Zettelkasten into a tremendous tool for creativity. After all, creativity is nothing more than connecting ideas. All novel ideas are based on previous ones. A piano plus writing is a typewriter, a telephone plus a printer is a fax machine, the idea of an office desk with files and folders combined with a television screen and a computer is a computer’s graphical desktop interface. Every novel idea is a remix and a Zettelkasten’s explicit purpose is to remix ideas.

The Zettelkasten principles

A Zettelkasten is a phenomenal tool for storing and organizing your knowledge, extending your memory, generating new connections between ideas, and increasing your writing output. However, to make the most of a Zettelkasten, you should follow some key principles.

  1. The principle of atomicity: The term was coined by Christian Tietze. It means that each note should contain one idea and one idea only. This makes it possible to link ideas with a laser focus.
  2. The principle of autonomy: Each note should be autonomous, meaning it should be self-contained and comprehensible on its own. This allows notes to be moved, processed, separated, and concatenated independently of its neighbors. It also ensures that notes remain useful even if the original source of information disappears.
  3. Always link your notes: Whenever you add a note, make sure to link it to already existing notes. Avoid notes that are disconnected from other notes. As Luhmann himself put it, “each note is just an element that derives its quality from the network of links in the system. A note that is not connected to the network will be lost, will be forgotten by the Zettelkasten” (original in German).
  4. Explain why you’re linking notes: Whenever you are connecting two notes by a link, make sure to briefly explain why you are linking them. Otherwise, years down the road when you revisit your notes, you may have no idea why you connected them.
  5. Use your own words: Don’t copy and paste. If you come across an interesting idea and want to add it to your Zettelkasten, you must express that idea with your own words, in a way that you’ll be sure to understand years later. Don’t turn your Zettelkasten into a dump of copy-and-pasted information.
  6. Keep references: Always add references to your notes so that you know where you got an idea from. This prevents plagiarism and makes it easy for you to revisit the original source later on.
  7. Add your own thoughts to the Zettelkasten: If you have thoughts of your own, add them to the Zettelkasten as notes while keeping in mind the principle of atomicity, autonomy, and the need for linking.
  8. Don’t worry about structure: Don’t worry about putting notes in neat folders or into unique preconceived categories. As Schmidt put it, in a Zettelkasten “there are no privileged positions” and “there is no top and no bottom.” The organization develops organically.
  9. Add connection notes: As you begin to see connections among seemingly random notes, create connection notes, that is, specific notes whose purpose is to link together other notes and explain their relationship.
  10. Add outline notes: As ideas begin to coalesce into themes, create outline notes. An outline note is a note that simply contains a sequence of links to other notes, putting those other notes into a particular order to create a story, narrative, or argument.
  11. Never delete: Don’t delete old notes. Instead, link to new notes that explain what’s wrong with the old ones. In that way, your Zettelkasten will reflect how your thinking has evolved over time, which will prevent hindsight bias. Moreover, if you don’t delete, you might revisit old ideas that may turn out to be correct after all.
  12. Add notes without fear: You can never have too much information in your Zettelkasten. At worst, you’ll add notes that won’t be of immediate use. But adding more notes will never break your Zettelkasten or interfere with its proper operation. Remember, Luhmann had 90,000 notes in his Zettelkasten!

How to implement a Zettelkasten

If you followed along this far, maybe you’re already excited to start your own Zettelkasten. If so, I have good news. You can start right now. You don’t need to buy some expensive software or, God forbid, a big clunky set of wooden drawers like Luhmann’s original Zettelkasten.

Paper-based solution

If you want to go old school and implement a paper-based solution, all you got to do is get a shoebox or similar container and a set of index cards or paper that you’ve cut up into appropriate sizes. Then start reading or thinking and each time you stumble across a new idea you want to keep track of, write it down on a separate index card. In one corner of the index card, add a unique identifier. Luhmann kept it simple and simply enumerated all his cards. If you want to follow that approach, then the first card you create would have the number 1, the second card would have the number 2, and so forth:

If at a later time you want to insert a bunch of new cards between the one numbered 1 and the one numbered 2, just place the new cards in between, giving them as identifiers 1/1, 1/2, 1/3, and so forth:

By adding a further slash, you can add additional cards between the newly created cards. For instance, to insert new cards between those numbered 1/1 and 1/2, label the new ones as 1/1/1, 1/1/2, 1/1/3, and so forth:

Now, to create links between two cards you simply use the identifiers. For instance, if you want to create a link from the card 1/1 to the card 1, simply write the number 1 somewhere on card 1/1. Similarly, if you want to create a link from card 23 to card 2, write 2 somewhere on card 23. By proceeding in this way, you can link your cards as you please:

If you want to add tags to your cards, simply write them on the cards themselves:

And to make it easier for yourself to find cards with a particular tag, create another note where you list all the tags you’ve used, with each tag followed by a list of identifiers corresponding to notes that match the given tag:

And that’s it! That’s a basic implementation of the Zettelkasten method using just paper index cards. Luhmann did essentially this, although he used an alphanumeric numbering system to identify his cards as he found a combination of numbers and letters easier to work with. If you’re curious, you can browse his cards here (although note that the cards are in German as that’s the language he wrote in).

Digital solutions

If you want to go digital, you have several options. You can use an app like Roam Research, Zettlr, Evernote, 1Writer, iA Writer, or any of the apps listed at zettelkasten.de. You can also use a personal wiki, plugins for text editors such as vim and sublime, or go for a combination of analog and digital where you write your notes on paper and then scan them.

Since a Zettelkasten is supposed to be used for a lifetime, I would definitely go with something that’s future proof and doesn’t have any vendor lock-in. I personally chose a plain text solution.

My Zettelkasten is a folder in Dropbox. This allows me to access my Zettelkasten from my computer, my phone, or any web browser. Each note is a separate text file kept within that folder. There are no subfolders. Everything is kept flat.

Whenever I create a new note, I create a new text file, whose filename is given by a timestamp followed by a title, as advocated by Christian from zettelkasten.de. For instance, right now it’s 16 December 2019 and the time is 13:52h. So if I were to create a note titled “Zettelkasten is amazing”, it would become a new text file named 201912161352-Zettelkasten-is-amazing.txt.

I then write the contents of the note using a combination of markdown and wiki-style double-bracket links. So the file 201912161352-Zettelkasten-is-amazing.txt might contain the following:

# 201912161352 Zettelkasten is amazing
#notetaking #writing #productivityThe Zettelkasten notetaking system is the best notetaking system ever.## Links
– [[201912070830-Zettelkasten-principles]]
– [[201912080935-Niklas-Luhmann-short-biography]]

The first line is the title of the note, the second line is a list of three hashtags, the next line is the idea I’ve written down, and the last two lines are links to two files: 201912070830-Zettelkasten-principles.txt and 201912080935-Niklas-Luhmann-short-biography.txt. Since the file is just plain text, it can be opened with any text editor on essentially any computer, phone, or tablet. That makes it future proof and independent of any particular application. But if you have a nice text editor that supports markdown and wiki-style double-bracket links, you can see your note nicely formatted. For instance, with 1Writer for iPad, the note looks like this:

Tapping on one of the blue links, opens the appropriate file. This makes it very convenient to browse the Zettelkasten. However, I could just as well use another text editor that supports markdown and wiki-style links or even use one that doesn’t support these features. In the latter case I would just select the text between double brackets, press ctrl c to copy the name of the file I want to open, and then just press ctrl v to paste the filename into whatever tool I want to use to open the text file.

Wrapping up

Luhmann’s Zettelkasten differs from other notetaking systems. Instead of being intended only as an aid for the next writing project, the method is designed to help you with a lifetime of thinking, writing, and publishing. It’s designed to accommodate as many notes as you want without turning into an unworkable mess. And it’s main purpose is to find connections among seemingly unconnected ideas.

Because of this, Luhmann rejected organizing his notes in a merely linear way or according to fixed categories. Instead, he organized his notes as a network of ideas that grows organically.

As you apply the method yourself, you’ll come across ideas that are glued to books, notebooks, web pages, newspapers, and other sources. With the Zettelkasten method it’s your job to liberate those ideas from their sources and turn them into notes that live in your central repository — in your Zettelkasten — where they are then linked to other notes. Essentially, you’re creating a collection of ideas where there are no boundaries between types of ideas and no boundaries between old and new ideas. Every idea can easily intermingle with any other to give rise to new ideas. That clearly distinguishes it from other notetaking methods based on notebooks, folders, or tags.

So if you care about remembering the ideas you encounter, if you care about how ideas relate to each other, and if you care about having ideas of your own, try the Zettelkasten method. It’s been specifically designed to manage ideas at a large scale and it made Luhmann one hell of a prolific writer.

David B. Clear is a writer, science fan, skeptic, and PhD. You can follow all his writing by subscribing to his newsletter.


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