Understanding Zettelkasten — What does it mean to communicate with the slip-box

Eva Thomas
10 min readAug 17, 2020
Zettelkasten method photo of the zettelkasten or slip-box with notes
Eva’s slip-box | Image provided by the author

I was sitting at my desk, looking at the small box full of my thoughts, filled with disappointment.

My slip-box is 3 months old, it contains a little over 100 notes, and it doesn’t work. I followed all rules and principles, and yet somewhere in the process I messed up. What went wrong?

Shifting mindset: from note-taking to communicating

Zettelkasten is usually mentioned as a note-taking method. However, the end goal of Zettelkasten is not gathering and collecting notes, but rather creating a competent and knowledgeable communication partner.

The main interaction with the slip-box is not when we are writing and adding new notes, because the slip-box is not there to be an archive of our memory and knowledge. Slip-box is there to be an apparatus with which we think. Therefore, the main interaction is when we communicate with the slip-box by confronting ourselves and our thinking with our prior knowledge.

The internal structure of the slip-box, based on the network of links between notes, turns the slip-box from a collection of notes into an interactive thinking partner that can give us surprising and unexpected responses and insights as a result of our interaction.

Luhmann believed that the only way to create a communication partner that will be increasingly valuable with time is to keep notes organization open.

Open organization: disorder with consistent internal structure

“For the internal organization of the slip-box and arrangement of notes, it is paramount that we decide against the order and categorization by topics and subtopics. Instead, we choose disorder and fixed location for each card”
—Niklas Luhmann

Luhmann organized notes by putting them one after the other. The decision about where the note will be placed wasn’t made because it fits organizationally to that location, but because it is contextually congruent with the preceding note.

Zettelkasten note example with ID
IDs are positioned in the top-left corner to be more visible | Image provided by the author

Each note in his slip-box has a unique alpha-numerical sequence that represents the position of the card inside the slip box, ensuring that the card will be accessible in the future. Also, this unique address is used on other cards as a reference.

Without fixed IDs and positions, note would be lost. We will never see it again, unless we stumble upon it accidentally, no matter how good or relevant the idea written on the note is. The slip-box forgets notes that are not an integral part of the web of interconnected slips.

If we want to place a new note between notes 4 and 5, a new note becomes 4a. 4a can be supplemented by 4a1 and so on. Luhmann called this internal branching. The internal structure is organized in this way so that we can create as many branches as we want, indefinitely.

Zettelkasten method nesting illustration with alpha-numerical IDs
Internal Branching | Image provided by the author

IDs are abstracted from any content-based order. The order that will emerge from them is merely formal. Avoiding premature systematization and fixed order is a prerequisite for a system that is supposed to support and enable creative thinking. Luhmann explained that defining an outline for our notes would imply committing to a specific sequence once and for all, and this kind of organization cannot adapt to the ongoing evolution of our thinking.

Multi-storage principle: card can be stored in multiple positions

Sometimes a new note will be contextually related to more than one note. In that case we will have multiple choices for its location. Rewriting the same card to keep it in more than one location would be tedious and useless in the long run. Therefore, in the physical slip-box, we must choose one position as a physical location of the card, and we will denote other choices by adding references to the card. The beauty of the Zettelkasten is that we don’t have to choose just one option — a new note can be stored in all relevant locations.

Zettelkasten method multiple storage illustration
Multiple Storage | Image provided by the author

Folgezettel deception: all references are created equal

IDs can have an additional function: to indicate that certain notes are part of the same sequence. For example, every note that begins with 4a7, like 4a7a, 4a7b, 4a7b1, can be considered as a link in a long chain of thoughts. I believed that notes in the chain have a specific type of connection, different than references written on cards. Therefore, I thought these sequences are an important structural concept.

However, Luhmann pointed out that the position of a single note in the physical slip-box is not privileged. We need to place the note somewhere. The references on the note will indicate other possible positions, but the fact that we have to pick one position as its primary physical location doesn’t mean that this specific location, or relation with surrounding cards, is more significant compared to other references.

“If there are several possibilities, we can solve the problem as we wish and just record the connection by a link”
— Niklas Luhmann

Understanding that location of the note doesn’t indicate special reference, and that relation to surrounding notes is not privileged was a significant revelation for me. My perspective about connections changed. When we look at the note to seek for relevant references, we must evaluate references with surrounding notes and those written on the card equally.

Smarter Folgezettels: keeping track of all contexts

Keeping track of sequences is beneficial because we can use a long thread of thoughts for our writing. It is ready for us — we don’t have to re-read a stack of notes to assemble a coherent combination of arguments. Luckily, IDs are not the only way. Luhmann used separate notes to keep track of sequences. He would add a title or a keyword to the top, elaborating on what concept he is specifying with the outline by writing a list of notes with their corresponding IDs and titles. Using separate notes for this is practical because it allows us to keep track of all sequences of the same note.

In digital databases, we can use Search to pull all sequences and branches related to the note - hence it is less likely that we will neglect branches, only because notes are scattered. However, in the physical Zettelkasten, we are not able to track all sequences with IDs. This can defeat open organization, and has the potential to hurt future discoveries if we are not careful.

References: the core of Zettelkasten

Luhmann considered referencing to be the crucial feature of his system. He believed that the quality of the note is determined by the quality, not quantity, of its references. Quality comes from the network of links with other notes, not from the content itself, because following the links through the web of thoughts will enrich our thinking with unexpected discoveries in a way re-reading the content of separated notes never will.

The purpose of internal references between cards is not to accumulate ideas around a broad concept, but to ensure unexpected insights. Therefore, references must be very selective.

“The references must not capture collective concepts that aggregate key aspects but must selectively lead away from the material subsumed under them”
— Niklas Luhmann

Luhmann emphasized that it is important that the context in which we add new ideas doesn’t predetermine the context of our future questions and queries. Therefore, we should think of references as breadcrumbs that we will be able to follow 20 years from now and still be able to find something that will make sense even if our point of view changes.

Re-defining “selective”: contextually congruent notes

The reference represents more than just a relation between two notes. It says that two notes are contextually congruent. I learned the hard way that the difference, though subtle, is very important.

Zettelkasten method illustration of contextual congruence of two notes
Contextually Congruent Notes | Image provided by the author

Two notes are contextually congruent if you can use their combination to answer a question or to solve a problem. For example, they can be a part of the same paragraph in an article, one of them can be used as an example, an argument, a clarification, or a metaphor for the other.

However, if they are just related, but not contextually harmonious, they might tackle a similar topic or share the same keyword, but their combination doesn’t carry greater meaning than their individual meanings. This is an important aspect that distinguishes the Zettelkasten from a Wiki database.

“The connections that already exist are, of course, selective. They do not fall into the limits of what is obvious, because we must close the gap between the one who takes note and the notes collection. If we are working toward the communication with the slip box, we must look for references which are unexpected. It is worthwhile to think of problems that connect disparate thoughts.”
— Niklas Luhmann

Two notes connected with a reference, when observed as a combination, can rise to a higher abstraction level than each one of them individually. For example, if I have a note that defines communication as an exchange of information and thoughts where partners can surprise and teach each other, and I have a note that says that internal structure of the Zettelkasten can cultivate creativity by revealing surprising connections between notes independent of the original references when the notes were initially created — I can combine these two into an argument that Zettelksten can act as a communication partner. But if I look for references only in the same area of interest, I am limiting the potential for future discoveries.

While creating a new reference we must ask ourselves: in what context these two notes can be combined in a meaningful way? The reference is good if we can elaborate. If we are struggling to make sense of this connection beyond topics and keywords — we have to think more. I am not saying to disregard the reference, but be selective and critical.

If the goal is to develop a communication partner, we must seek relations by thinking of problems and questions that connect ideas and arguments that have no straightforward or obvious relation. It will provide combinations of ideas that were never planned or preconceived.

Quality over quantity: build a map, not a maze

The surprises we encounter while interacting with the slip-box Luhmann described as a process of finding something you were not looking for, but something that you can still use. There is no point in finding idea out of context that has no value to our current questions. This is why it is important to form references around shared context, not around general and broad concepts that are relevant to too many other notes.

Otherwise, we are creating references that won’t be guidelines, but a source of distraction. If you are trying to examine your slip-box with a specific ask, and you go through your notes, but you have so many connections and so many of them are vague and general, you will spend so much time re-reading them to find something purposeful, that you will probably get distracted or lose interest altogether.

This is the reason why the context in which we decide to place the note by adding references to it initially shouldn’t hinder the context of future queries. The only way to ensure this is to avoid the categorization of notes and to use context-specific references.

Innovation tool: ask the slip-box

The references we can make when we are adding a note to the slip-box won’t be the same as those we discover while we search with a specific question in mind. Through this process, we can find new connections between previously unrelated notes and to create something that Luhmann named “relations of relations”.

“The communication with the slip box becomes rewarding only at a high level of generalization, specifically while unveiling relations of relations. And it becomes valuable only at the moment of observation, thus it is bound to a specific moment and is to a high degree accidental.”
— Niklas Luhmann

When we write an article, it represents the current state of our thoughts. Ideas we decide to use as building blocks for the article can be a result of accidental relations we discovered. They don’t have to be in the slip-box in the form of a note or reference. Our writing is not a result of simply copying what is already in the slip-box. True value of the slip-box becomes clear when we combine ideas and take them to the higher level of abstraction to articulate an answer to our question by creating relations of relations type of references between previously unconnected ideas, references relevant to that specific query that couldn’t be anticipated before. This is why we refer to it as an unexpected discovery or accidental insight.

We can use these insights as new notes and add them to the slip-box. By doing that we are actively engaging with the slip-box, we are refining our arguments and thinking, while feeding the slip-box with new references and new ideas — we are communicating.

In 1981. Niklas Luhmann, author of the original Zettelkasten, wrote a paper: “Communication with note boxes,” where he described and explained his note-taking method. This paper is the main reference I used to review my assumptions and to expose cracks in my understanding. Explanations I found in a chapter from the “Forgetting Machines: Knowledge Management Evolution in Early Modern Europe” book with title: “Niklas Luhmann’s Card Index: Thinking Tool, Communication Partner, Publication Machine” written by Johannes F. K. Schmidt was very helpful, especially for overcoming false assumptions and misconceptions.

Eva Thomas

Aspiring learner, passionate about physics, math and the world in between, writing about personal experiences, sharing inspiring discoveries