Excerpts from How To Take Smart Notes

APRIL 1, 2020

I looked at Sönke Ahrens’ How To Take Smart Notes because I was interested in the Zettelkasten methodology the book explains (more on Zettelkasten in an upcoming post). The book is a mixture of a summary of Zettelkasten plus misc opinions on the importance of note-taking and tips on motivation / writing (I found the latter less useful!). Overall this is a reasonable introduction, though if you just want an intro to Zettelkasten there are probably shorter ones out there.



Writing is important and note taking is important to writing => note taking is important

Good, productive writing is based on good note-taking. Getting something that is already written into another written piece is incomparably easier than assembling everything in your mind and then trying to retrieve it from there.

The quality of a paper and the ease with which it is written depends more than anything on what you have done in writing before you even made a decision on the topic.

Everything You Need to Know

Storing notes in folders gets complicated and reduces opportunities to make connections

Most people try to reduce complexity by separating what they have into smaller stacks, piles or separate folders…which makes it look less complex, but quickly becomes very complicated. Plus, it reduces the likelihood of building and finding surprising connections between the notes themselves.

Luhmann’s method involved two slip-boxes: one box for bibliographic notes and notes on books he read, the other for his own ideas


Strictly speaking, Luhmann had two slip-boxes: a bibliographical one, which contained the references and brief notes on the content of the literature, and the main one in which he collected and generated his ideas, mainly in response to what he read. The notes were written on index cards and stored in wooden boxes.

Whenever he read something, he would write the bibliographic information on one side of a card and make brief notes about the content on the other side (Schmidt 2013, 170). These notes would end up in the bibliographic slip-box.

In a second step, shortly after, he would look at his brief notes and think about their relevance for his own thinking and writing. He then would turn to the main slip-box and write his ideas, comments and thoughts on new pieces of paper, using only one for each idea and restricting himself to one side of the paper, to make it easier to read them later without having to take them out of the box. He kept them usually brief enough to make one idea fit on a single sheet, but would sometimes add another note to extend a thought.

He usually wrote his notes with an eye towards already existing notes in the slip-box. And while the notes on the literature were brief, he wrote them with great care, not much different from his style in the final manuscript…More often than not, a new note would directly follow up on another note and would become part of a longer chain of notes. He then would add references to notes somewhere else in the slip-box, some of them which were located nearby, others in completely different areas and contexts. Some were directly related and read more like comments, others contained not-so-obvious connections. Rarely would a note stay in isolation.

Luhmann used an alphanumeric string to identify each note


The trick is that he did not organise his notes by topic, but in the rather abstract way of giving them fixed numbers. The numbers bore no meaning and were only there to identify each note permanently. If a new note was relevant or directly referred to an already existing note, such as a comment, correction or addition, he added it directly behind the previous note. If the existing note had the number 22, the new note would become note number 23. If 23 already existed, he named the new note 22a. By alternating numbers and letters, with some slashes and commas in between, he was able to branch out into as many strings of “thought as he liked. For example, a note about causality and systems theory carried the number 21/3d7a7 following a note with the number 21/3d7a6.


Whenever he added a note, he checked his slip-box for other relevant notes to make possible connections between them. Adding a note directly behind another note is only one way of doing this. Another way is by adding a link on this and/or the other note, which could be anywhere in the system. This very much resembles, of course, the way we use hyperlinks on the internet. But, as I will explain later, they are quite different and it would be rather misleading to think of his slip-box as a personal Wikipedia or a database on paper. The similarities are obviously there, but the subtle differences are what makes this system unique.

By adding these links between notes, Luhmann was able to add the same note to different contexts. While other systems start with a preconceived order of topics, 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.

The last element in his file system was an index, from which he would refer to one or two notes that would serve as a kind of entry point into a line of thought or topic. Notes with a sorted collection of links are, of course, good entry points.

Everything You Need to Do

3 different types of notes: fleeting, literature, permanent


  1. Make fleeting notes [as] reminders…and process them later.

  2. Make literature notes. Whenever you read something, make notes about the content. Write down what you don’t want to forget or think you might use in your own thinking or writing. Keep it very short, be extremely selective, and use your own words. Be extra selective with quotes – don’t copy them to skip the step of really understanding what they mean. Keep these notes together with the bibliographic details in one place – your reference system.

  3. Make permanent notes…Go through the notes you made in step one or two (ideally once a day and before you forget what you meant) and think about how they relate to what is relevant for your own research, thinking or interests. This can soon be done by looking into the slip-box – it only contains what interests you anyway. Write exactly 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. Throw away the fleeting notes from step one and put the literature notes from step two into your reference system.

  1. Now add your new permanent notes to the slip-box by: > > a) Filing each one behind one or more related notes (with a program, you can put one note “behind” multiple notes; if you use pen and paper like Luhmann, you have to decide where it fits best and add manual links to the other notes). Look to which note the new one directly relates or, if it does not relate directly to any other note yet, just file it behind the last one. > > b) Adding links to related notes. > > c) Making sure you will be able to find this note later by either linking to it from your index or by making a link to it on a note that you use as an entry point to a discussion or topic and is itself linked to the index.

Use the slip-box to guide the direction your research takes

  1. Develop your topics, questions and research projects bottom up from within the system. See what is there, what is missing and what questions arise. Read more to challenge and strengthen your arguments and change and develop your arguments according to the new information you are learning about.

Join notes together into a topic, refine and refine and … voila an essay is born!

  1. After a while, you will have developed ideas far enough to decide on a topic to write about. Your topic is now based on what you have, not based on an unfounded idea about what the literature you are about to read might provide. Look through the connections and collect all the relevant notes on this topic (most of the relevant notes will already be in partial order), copy them onto your “desktop” and bring them in order. Look for what is missing and what is redundant. Don’t wait until you have everything together. Rather, try ideas out and give yourself enough time to go back to reading and note-taking to improve your ideas, arguments and their structure.

  2. Turn your notes into a rough draft. Don’t simply copy your notes into a manuscript. Translate them into something coherent and embed them into the context of your argument while you build your argument out of the notes at the same time. Detect holes in your argument, fill them or change your argument.

  3. Edit and proofread your manuscript.

A typical work day will contain many, if not all, of these steps: You read and take notes. You build connections within the slip-box, which in itself will spark new ideas. You write them down and add them to the discussion. You write on your paper, notice a hole in the argument and have another look in the file system for the missing link. You follow up on a footnote, go back to research and might add a fitting quote to one of your papers in the making.

Everything You Need to Have: Tools

Good tools reduce distraction

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. The slip-box provides an external scaffold to think in and helps with those tasks our brains are not very good at, most of all objective storage of information.

We need four tools: writing tool, reference system, main slipbox and editor (for producing finished pieces of writing)


  • Something to write with and something to write on (pen and paper will do)
  • A reference management system (the best programs are free)
  • The slip-box (the best program is free)
  • An editor (whatever works best for you: very good ones are free)

The reference system is like Luhmann’s bibliographic slip-box

The reference system has two purposes: to collect the references (duh) and the notes you take during your reading. I strongly recommend using a free program like Zotero.

Ahrens recommends a digital tool for the slip-box (but looks not updated since 2015)

I strongly recommend using Daniel Lüdecke’s Zettelkasten. It is the only program I know that really implements the principles behind Luhmann’s system and is at the same time simple and easy to use.

The Four Underlying Principles

Simplicity Is Paramount

The conventional way of taking notes isn’t optimised to support the writing which follows

Many students and academic writers…handle their ideas and findings in the way it makes immediate sense: if they read an interesting sentence, they underline it. If they have a comment to make, they write it into the margins. If they have an idea, they write it into their notebook, and if an article seems important enough, they make the effort and write an excerpt. Working like this will leave you with a lot of different notes in many different places. Writing, then, means to rely heavily on your brain to remember where and when these notes were written down.

Most students sort their material by topic or even by seminars and semester (which makes no sense if you think about it)

But with a slipbox all notes are processed and stored in the same way and cross-pollination of ideas is more likely


everything goes into the same slip-box and is standardised into the same format…It is the standardised format that enables the notes to build up a critical mass in one place. It is also the key to facilitating the thinking and writing process by removing all unnecessary complications or decisions that come with a variety of different formats and storage places. Only because every note is in the same format at the same place can they later be combined and assembled into something new and no thought is ever wasted on the question of where to put or label it.

Project notes are notes for specific projects that won’t be useful once it’s finished. They can be kept with the project (cf GTD)


The last type of note, the ones that are related to only one specific project, are kept together with other project-related notes in a project-specific folder. It doesn’t matter in which format these notes are as they are going to end up in the bin after the project is finished anyway (or in an archive – the bin for the indecisive).

Nobody Ever Starts From Scratch

A slip-box is an accumulation of ideas long before the writing of e.g. a paper begins


If we look into our slip-box to see where clusters have built up, we not only see possible topics, but topics we have already worked on – even if we were not able to see it up front. The idea that nobody ever starts from scratch suddenly becomes very concrete. If we take it seriously and work accordingly, we literally never have to start from scratch again.

Let the Work Carry You Forward

Feedback increases motivation, the process of writing and connecting notes increases feedback


Expressing our own thoughts in writing makes us realise if we really thought them through. The moment we try to combine them with previously written notes, the system will unambiguously show us contradictions, inconsistencies and repetitions. While these built-in feedback loops do not make redundant the feedback from your peers or supervisor, they are the only ones that are always available and can help us to improve a little bit, multiple times every single day.

The Six Steps to Successful Writing

Separate and Interlocking Tasks

The importance of having a work flow that is robust to our focus shifting

The first step is to break down the amorphous task of “writing” into smaller pieces of different tasks that can be finished in one go. The second step is to make sure we always write down the outcome of our thinking, including possible connections to further inquiries. As the outcome of each task is written down and possible connections become visible, it is easy to pick up the work any time where we left it without having to keep it in mind all the time. Possible subsequent tasks are open questions or connections to other notes, which we could elaborate on further or not. It also comes up in explicit reminders like “review this chapter and check for redundancies,” which belong into the project folder. Or the third option is the simple fact that something is still in our in-box waiting to be turned into a permanent note – a quick and not-yet–crossed-out note in our notebook, or literature notes not yet archived in our reference system.

Read For Understanding

Translating what you read into your own context creates something new

If you understand what you read and translate it into the different context of your own thinking, materialised in the slip-box, you cannot help but transform the findings and thoughts of others into something that is new and your own.

Engage with alternate views; aim to build a lively dialogue within the slip-box

The classic role model would be Charles Darwin. He forced himself to write down (and therefore elaborate on) the arguments that were the most critical of his theories. “I had […] during many years followed a golden rule, namely, that whenever a published fact, a new observation or thought came across me, which was opposed to my general results, to make a memorandum of it without fail and at once; for I had found by experience that such facts and thoughts were far more apt to escape from the memory than favorable ones. Owing to this habit, very few objections were raised against my views, which I had not at least noticed and attempted to answer.” (Darwin 1958, 123)

Rewording text helps reveal what is being said (and left out)

“Probably the best method is to take notes – not excerpts, but condensed reformulated accounts of a text. Rewriting what was already written almost automatically trains one to shift the attention towards frames, patterns and categories in the observations, or the conditions/assumptions, which enable certain, but not other descriptions.(Luhmann 2000, 154f)”

Take Smart Notes

Creating literature notes gives feedback on - and improves - our understanding of the text

Taking literature notes is a form of deliberate practice as it gives us feedback on our understanding or lack of it, while the effort to put into our own words the gist of something is at the same time the best approach to understanding what we read.

Develop Ideas

Luhmann used alphanumeric strings to identify and sequence notes


Ideally, new notes are written with explicit reference to already existing notes. Obviously, this is not always possible, especially in the beginning when the slip-box is still in its infancy, but it will very soon become the first option most of the time. Then you can put the new note “behind” an existing, related note straight away. Luhmann, working with pen and paper, would put a note behind an existing one and number it accordingly. If the existing note bore the number 21, he numbered the new note 22. If note number 22 already existed, he would still add it behind 21, but number it 21a. By alternating numbers and letters, he was able to branch out into an infinite number of sequences and sub-sequences internally with no hierarchical order.

An initial subsequence that attracts more and more follow-up notes can easily become a main topic with many subtopics over time (Schmidt 2013, 172). The digital Zettelkasten makes things easier: numbers are assigned automatically, note sequences can be constructed any time later and one note can become the follow-up note to different notes at the same time.

Index cards contain keywords with the ID of one or two notes next to each keyword, providing a ‘way in’ to topics in the slip-box


After adding a note to the slip-box, we need to make sure it can be found again. This is what the index is for. Luhmann wrote an index with a typewriter on index cards. Luhmann would add the number of one or two (rarely more) notes next to a keyword in the index (Schmidt 2013, 171).

Most notes will be found through other notes. The organisation of the notes is in the network of references in the slip-box, so all we need from the index are entry points. A few wisely chosen notes are sufficient for each entry point. The quicker we get from the index to the concrete notes, the quicker we move our attention from mentally preconceived ideas towards the fact-rich level of interconnected content, where we can conduct a fact-based dialogue with the slip-box.

Luhmann also created notes giving overviews of topics within the slipbox


Even though we will not get an overview of the whole slip-box (as we certainly will never get an overview of our whole internal memory), we can get an overview of a specific topic. But because the structure of topics and subtopics is not a given, but the outcome of our thinking, they too are subject to ongoing considerations and alteration. The consideration of how to structure a topic, therefore, belongs on notes as well – and not on a meta-hierarchical level. We can provide ourselves with a (temporarily valid) overview over a topic or subtopic just by making another note.

Choose keywords based on the projects and interests that a note is likely to be useful for


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. This is also why this process cannot be automated or delegated to a machine or program – it requires thinking.

Types of cross-referencing:


Luhmann used four basic types of cross-references in his file-box (Schmidt 2013, 173f; Schmidt 2015, 165f). Only the first and last are relevant for the digital Zettelkasten, the other two are merely compensating for restrictions of the analogue pen and paper version. You don’t need to concern yourself with them if you use the digital program.

1.    The first type of links are those on notes that are giving you the overview of a topic. These are notes directly referred to from the index and usually used as an entry point into a topic that has already developed to such a degree that an overview is needed or at least becomes helpful. On a note like this, you can collect links to other relevant notes to this topic or question, preferably with a short indication of what to find on these notes (one or two words or a short sentence is sufficient). This kind of note helps to structure thoughts and can be seen as an in-between step towards the development of a manuscript. Above all, they help orientate oneself within the slip-box.

2.    A similar though less crucial kind of link collection is on those notes that give an overview of a local, physical cluster of the slip-box. This is only necessary if you work with pen and paper like Luhmann. While the first type of note gives an overview of a topic, regardless of where the notes are located within the slip-box, this type of note is a pragmatic way of keeping track of all the different topics discussed on the notes that are physically close together. Obviously, we don’t need to worry about this if we work with the digital version.

3.    Equally less relevant for the digital version are those links that indicate the note to which the current note is a follow-up and those links that indicate the note that follows on the current note. Again, this is only relevant to see which notes follow each other, even if they don’t physically stand behind each other anymore. The digital Zettelkasten automatically adds these kinds of backlinks and presents you the relevant notes in a note sequence.

4.    Connection between two individual notes. By linking two related notes regardless of where they are within the slip-box or within different contexts, surprising new lines of thought can be established. These note-to-note links are like the “weak links” (Granovetter 1973) of social relationships we have with acquaintances: even though they are usually not the ones we turn to first, they often can offer new and different perspectives.

Write just one idea on each note:


even though the digital program lifts the physical restrictions on the length of a note, I highly recommend treating a digital note as if the space were limited. By restricting ourselves to one format, we also restrict ourselves to just one idea per note and force ourselves to be as precise and brief as possible.

Share Your Insight

Instead of brainstorming, make use of the accumulated insights in the slip-box

If we had a good idea before (and it is certainly more likely that we will come up with a good idea over the “course of several months rather than within a couple of minutes), it will be in there. It might even already have proved itself worthy of following up on, in which case it is already connected to supporting material. It is so much easier to see what worked than to predict what might work.

Work on several manuscripts at the same time to get the most out of research

While the slip-box is already helpful to get one project done, its real strength comes into play when we start working on multiple projects at the same time. The slip-box is in some way what the chemical industry calls “verbund.” This is a setup in which the inevitable by-product of one production line becomes the resource for another, which again produces by-products that can be used in other processes and so on, until a network of production lines becomes so efficiently intertwined that there is no chance of an isolated factory competing with it anymore.

Giving Up On Planning

Rapid feedback loops and segmenting tasks may help overcome planning fallacy

When the researchers checked how much time the students really needed, it was much, much longer than they estimated. Not even half of the students managed to finish their papers in the time they thought they would need under the worst possible conditions (Buehler, Griffin and Ross 1994).

In another study a year later, the psychologists looked more closely at this phenomenon, which still puzzled them because the students could have answered any way they liked – there was no benefit in giving overly optimistic answers. They asked the students to give them time ranges in which they were either 50%, 70% or 99% sure to finish their paper.

Again: They were free to give any answer. But, sure enough, only 45% managed to get their papers done within the time they were sure they had a 99% likelihood to finish it under any condition they regarded as possible (Buehler, Griffin, and Ross 1995)

The other lesson is not that we can’t learn from our experiences, but that we can only learn from our experiences if feedback follows shortly afterwards – and maybe more than once in a while. Disassembling the big challenge of “writing a paper” into small, manageable tasks helps to set realistic goals that can be checked on a regular basis.