July 7, 2020

Zettelkasten: Think inside the box

Let me ask you a question: What have you done with the text you’ve underlined in the book you’ve read recently? Have you revisited this other book with all the dog ears? In other words: Are you satisfied with how you manage your ideas and those you’ve read in books? Well, I wasn’t. But it changed two weeks ago.

Over the past few years, I’ve tried to come up with a system that would allow me to track the most salient ideas in the books I’ve read. I underlined, I used sticky tabs (I have a copy of Art and Technics by Lewis Mumford that looks like a Christmas tree), I’ve even tried to copy excerpts on index cards. Nothing worked: I felt like regardless of how much I read, my knowledge was as good as my memory, and it was like filling a leaky bucket.

Did you ever feel that way? I’ve got some good news. Read on.

Underlining doesn’t work

Sönke Ahrens wrote How to Take Smart Notes (affiliate link) for “Students, Academics, and Nonfiction Book Writers.” The tool at the core of the book is the Zettelkasten, or slip-box in German, as invented by Niklas Luhmann.

Luhmann was a prolific German sociologist who wrote more than 70 books and nearly 400 articles. He invented a way to think through writing, relying on rigorous and systematic note-taking: He’d write ideas on small index cards, number them, and file them in a drawer.

In his Zettelkasten method, there are three kinds of notes:

  • fleeting notes: the great idea that comes to you in the shower, or while commuting. All fleeting notes go to an inbox, and you review them within 48 hours. The lucky ones become permanent (more on them below).
  • literature notes: no more underlining! Every time you read something that you don’t want to forget, you have to rewrite it (and that’s key) in your own words to create a literature note. They are concise but in full prose, and rarely feature full quotes.
  • permanent notes: Only permanent notes are kept in the Zettelkasten. Fleeting or literature notes can become permanent notes if they contribute to the ongoing conversation of ideas happening in the Zettelkasten. What does this idea bring? Does it support an existing idea? Does it contradict another? Once a fleeting note becomes permanent, discard it. All literature notes, whether they were turned into permanent notes or not, go into your reference system.

Luhmann designed a smart way to number permanent notes and thread them. At the end of his career, his Zettelkasten contained 90,000 notes.

If you want to learn something for the long run, you have to write it down. If you want to really understand something, you have to translate it into your own words. —Sönke Ahrens

It’s not about the notes, though: A second brain

The Zettelkasten is more than a collection of index cards (paper or digital). It is a tool to augment our memory and our thinking. As Ahrens writes:

We need a reliable and simple external structure to think in that compensates for the limitations of our brains.

By systematically entering notes in a Zettelkasten, we make better use of our brains:

The slip-box is designed to present you with ideas you have already forgotten, allowing your brain to focus on thinking instead of remembering.

The Zettelkasten is a way to write from the bottom up; you don’t need to write a plan. Consult the box and follow a thread of pre-written arguments. Ideas are already written down in your own words, backed by references, and interconnected in a network that you built.

Because it’s been used by scholars, the Zettelkasten is focused on writing, but I believe that any creative (and as such, curious) person whose work depends on generating new ideas could benefit from it.

Build your own Zettelkasten

You could go paper, like Luhmann, but you would run the risk of losing your notes (if your data doesn’t exist in three places, it doesn’t exist at all).

I decided to go digital, and Sonke’s book introduces a series of tools for keeping notes and references.

For my reference system, I use Zotero, a “free, easy-to-use tool to help you collect, organize, cite, and share research.” It is available on Windows, Mac, and Linux, as well as a web app and browser extensions that let you add a reference from a web page. It is straightforward to add notes to each reference, whether it’s an article, a book, a podcast, etc. Oh, and try dragging and dropping an academic paper in PDF form inside Zotero and watch the application populate the metadata for you. It’s beautiful.

I picked Obsidian as my digital Zettelkasten (although Zettlr has some very powerful features, too). Just like Zotero, it is free (the dev team welcomes financial support) and it stores notes as Markdown files in a folder system. Linking notes is done through [[ ]] syntax, and a graph view shows how interconnected they are.

In Obsidian's Zettelkasten, text labels (notes) are interconnected to form a complex network of ideas.

In Obsidian’s Zettelkasten, text labels (notes) are interconnected to form a complex network of ideas. Source:

As you see, in Obsidian clusters are a visual way to detect ideas worth exploring, since they’re well connected.

I keep my notes in a Dropbox folder that I sync with my Mac, Windows, and Linux machines, so they’re always up-to-date and available on every machine in my house.

Building a Zettelkasten takes a while

I have a baby Zettelkasten, right now. A newborn, really. It will take a few years of nurturing to start having conversations inside and with the Zettelkasten. Keep this in mind if you expect insights to jump at you fast—they won’t.

But like anything worth doing in life, it’s about the process. How good could it make you feel to know that you’ve put some duct tape on that leaky bucket and that your knowledge improves instead of vanishing week after week?


Thomas Deneuville lives in Upstate NY with his wife and two sons, where he writes about creativity, draws, codes, and plays the bagpipe.

2 Comments on “Zettelkasten: Think inside the box

July 28, 2020 at 5:53 pm

hi mate could you help me with literature notes x permanent notes ? i can’t understand yet =(

Thomas Deneuville
July 29, 2020 at 10:04 am

Hello, Marcos! No problem. My understanding is that literature and permanent notes live in separate places. Literature notes are notes (in your own words) that you take while reading an article, a book, etc. They help you process what you’ve just read and act as a summary too.
Now, these literature notes will also spark new ideas—your ideas—that you will turn into permanent notes in your Zettelkasten. You can also reference literature notes in your permanent notes.
If you end up writing something that you’ll publish, it will be much easier for you to quote all of your sources appropriately. Does it make sense?

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.