Book Review - How to Take Smart Notes

This article is my review of the book How to Take Smart Notes.

Niklas Luhmann’s system

Niklas Luhmann was a German sociologist who invented a revolutionary way of organizing knowledge. He was an extremely prolific author, writing more than 70 books and nearly 400 papers.

He was able to be so efficient with the invention and use of the Slip Box (Zettelkasten), a note-taking system.

Luhmann's Zettelkasten

The Slip Box

Every day, whenever Luhmann learned something, he wrote it down, using paper cards in the A6 format.
Due to the paper size, each note was short and had to convey a single idea.

He then folded those cards into a box, sorting them by subject. If a note was directly related to another note, it came right behind it.

Each note also got a unique identifier, consisting in an incrementing integer. The first note was named 1. Any note coming after it would be named 2.
If he needed to add a new note between those two, he would name it 1a.

Since every note has a unique identifier, he could easily reference them together,

Each note was written without the context it came from. It conveyed a single idea, and was meant to make it possible to retrieve that idea quickly whenever the subject came up.

Why writers have the syndrom of a blank page

Whenever we want to write something, we tend to think the best way to do so is to take a pen and a sheet of paper, and write down whatever comes to our mind.

That’s the best way to end up not writing anything, as none of everything we studied on the subject we want to write about will come back to mind.

Using the slip box, notes will accrue over time with everything you study about any subject.
The day you want to start writing about something, all you have to do is pick up those notes, follow their trail and see where that leads you.

Even when starting a study on a new project, if you have a slip box going for quite some time, there may already be notes related to it for reading you did in the past and you have forgotten.

Learning vs Understanding

The entire basis of the Luhmann system revolved around learning vs understanding.

The process of learning is often considered as an accumulation of knowledge. The more you learn, the more you know and the more knowledgable you are.

However, this is not how the human brain works. While we can remember a lot of things, we can only keep 2 or 3 things at the same time at the top of our minds. Anything else will come as a cue due to links our brain makes between subjects.

The slip box allows someone to focus on understanding. In order to write down every idea which is being learned, we need to understand it, as we have to rephrase the subject in our own words.

The slip box also allows its owner to make better cues than what their brain would provide them, as the link between subjects is provided by the notes, not by the brain itself.

Focus on writing

Luhmann being an academic, his focus was on writing books and academic papers.

The slip box is great at doing that, as whenever he read a paper or a book, he wrote several notes about what he discovered in there. Those notes could either be directly the subject he was researching, or on another one he was interested in, or even on a subject he would become interested in later on.

Each note being a single idea, it had to be made very simple. The only way to explain something simply is to understand it. So by writing notes in his slip box, Luhmann made sure he understood the concepts he was studying.

Whenever Luhmann wanted to start writing a book or paper, he would collect his notes on the subject he had in mind and see where it would bring him.

The Zeigarnik Effect

Bluma Zeigarnik was a psychologist. She discovered that our brain tends to better remember uncompleted or interrupted tasks than completed ones.

The brain also tends to mistake writing down something with completing it.

By writing down things we learn, we therefore not only better understand them, it also allows our brain to move on to something else, which can always be brought back by looking at the note.

Applying the system

After explaining the concept behind Luhmann’s slip box, the book went on to giving tips to implement one’s own.

Always be Writing

The best way to start a slip box is to write. Whenever you read something, have a pen and paper (or a note-taking app) around to note anything that seems interesting or that you want to research deeper.

Then, at least once per day, go back to those notes and try to make them permanent.
A permanent note is one stripped of its context. You need to be able to come back to it in 5 years and still understand what idea it conveys.

Those permanent notes will go into your slip box. The temporary ones should be thrown out to avoid ending up with a pile of unsorted notes that you can’t even look into.


While Luhmann wrote all his notes on paper, digitalizing the system may make it easier to work with, as long as the system is generic enough not to come in the way of the writer.

There are many tools someone can use to write down their notes, the simplest could be a folder synchronized somewhere, with a note for each file. That would probably be a bit too cumbersome to maintain though.

Dedicated software such as The Archive also exist to make it easier to manage notes.


There are very few books that I read and realize they are going to drastically change something in my life.
It’s still too early to say, as I’ve started my own slip box only two weeks ago now, and as of the writing of this article, I only have 30 notes.

It’s, however, definitely the feeling I’m closing this book with. I want to write notes, and see if following their trail helps me in writing (text or code).

So far, I have started my slip box as a GIT repository. Each note is written in markdown, and they all have a title as well as a couple tags.
The README contains an auto-generated index sorted by tags, which helps me link notes together easily.

Now, to write, and see how this goes for several months!