What is Zettelkasten? A Book Review of ‘How to Take Smart Notes’ by Sönke Ahrens

This book is the best book in the English language on the Zettelkasten information storage technique, mostly because it is the only in the English language on Zettelkasten, which is the German word for “slip-box”—as in a box where index cards are stored. 20th-century social scientist Niklas Luhmann who used this technique to write 70 books and more than 400 scholarly articles in his 40 years of academia.

How can index cards provide this level of productivity?

The concept of the Zettelkasten isn’t difficult in theory but can get complicated in practice.

As he would read, Luhman would find facts or thoughts he wanted to remember and rewrite those ideas on an individual card in his own words with a bibliography source on the back of the card. Each card would only contain one “atomized thought” that was written so that the thought could be understood on its own apart from other contextual cards.

On the front of the card, he would give a unique number and write links to other related cards. As an example, if he had a card on the Dunning-Krueger Effect (DKE), it might be labelled #42 and a study he found that proved the DKE within a particular field might be #42A and another study that linked to the first might be written on #42A1. In the days before the rise of the internet, having a web of hyperlinked analog notes allowed Luhmann to integrate each new thought into his “external brain” and often the connections he would go through while categorizing new documents would inspire new connections between old ideas.

This video shows Luhmann’s Zettelkasten, all 90,000+ cards. It is in German with Japanese subtitles, but you can change the subtitles to English under the gear-shaped settings icon.

Luhmann started his career with a law degree and working in civil service. After his 9-5 job, he’d come home and consume sociology books, adding the notes to his zettelkasten. After a few years of this, he had published a few books and was asked to become a professor of sociology, but he had no PhD. He spent a year working with his zettelkasten and produced his PhD thesis.

What can this crazy German card box system offer me?

Sure, that was great for Luhmann, but what can a zettlekasten offer us in the 21st century? I have a great many methods of preserving electronic and analog notes, but they’ve always remained random collections of information that were never synthesized into a whole. The categorization process of building a zettlekasten along with rewriting others thoughts in your own words offers a way to learn and combine ideas that has had a huge productivity boost for many who have tried it. Many who use a zettelkasten now use electronic tools to aid in categorization, hyperlinking, and tagging. There are both purpose built apps (many of them built on plain text formats to avoid fears of file obsolescence) as well as people creating plugins for SublimeText, nvALT, VIM, Emacs, etc. to use as zettelkasten. Most of the material is still in German only, so it’s been a slow process to gain traction in the English speaking world, but more and more productivity writers are singing the praises of the system, especially for those in academia.

The book convinced me to give it a try, and I’ve created an analog card system. I’m on day 2 and I have 9 cards so far, so we’ll see if I’ve stuck with it after a month, but so far I’ve found it a handy discipline. I’ve also found that if I want to remember something, writing it down by hand helps to encode it in my memory much more than typing, so even if I end up moving to a digital zettelkasten, this has been a good experience.

Some of the cards in the early days of my analog Zettelkasten experiment.

I highly recommend buying this slim volume for $12 if the idea of a zettlekasten intrigues you, but I also wanted to share many of the other great links I found traveling down this rabbit hole. The book breaks down each of the aspects of the system and includes many interesting studies and stories that illustrate the principles behind zettelkasten. You can also read the first chapter at the author’s website.

Additional Resources

  • Medium Article Zettelkasten – How One German Scholar Was So Freakishly Productive by David B. Clear – this was my introduction to the world of Zettelkasten and it is a wonderfully-written way to learn what is unique about the system and whether or not it is right for you.
  • LessWrong ArticleThe Zettelkasten Method by abramdemski – this is a great deep dive on how the system works and how to explore it using analog cards that is hosted on LessWrong. If this is too much, there is also a good shorter post on LessWrong about How to take smart notes.
  • EssayCommunicating with Slip Boxes: An Empirical Account by Niklas Luhmann –
  • BlogZettelkasten.de – the best English-language site for Zettelkasten, but it’s hard to get a good overview of the system from this site. I’d save this to come back to after you know the basics. Note that the two gentlemen who run this blog also produce The Archive, an electric Zettelkasten app for $20. I have not used it, so I cannot vouch for its quality or lack thereof, but it seems like an interesting option to explore!
  • ArticleLiving with a Zettelkasten by Magnus Eriksson – another good overview and fills in a bit more resolution.
  • HackerNews ForumZettelkasten? An interesting topic that considers many similar methods of information storage and retrieval.
  • Subreddit/r/Zettelkasten – not a ton of activity, but it can be a good place to find other implementation.
  • WebsiteTakeSmartNotes – the Author’s website, with a lot of extra material. Check out the Tools page.

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