Zettelkasten

Among the seemingly thousands of blog posts, YouTube videos, and books on the Zettelkasten note taking system, there seems to be very little clear advice on what Zettelkasten actually is and why it would be useful. Instead any internet search about the topic is clogged up with descriptions of how "life changing" a given note taking app is, with people putting calendars, maps, and even databases in their Obsidian and Notion notes.

From the perspective of the reader, this eventually just descends into a pernicious form of productivity porn, where simply reading about the often insane things people are doing with their "plain text" notes gives the feeling of being productive, whilst spending little to no time focussing on the content of the notes, or the thing to be studied or created.

However, like the majority of ideas about how to be productive that have created an industry of charlatans, the useful core of the idea can be described in no more than a short blog post. As such, this post is my extremely brief description of the what, why, and how of Zettelkasten, without all the cruft.

What?

Zettelkasten is a note taking system with (usually) two defining features,

1. notes are small, and typically focus on a single idea,
2. when a note needs to refer to another, it contains a link or reference to said note.

In it's original form, a Zettelkasten was a collection of index cards, each with a unique ID. Links between notes were just references to other notes by their ID. Nowadays, there are apps designed around making the management of links better, and keeping notes stored digitally.

The digital incarnation of Zettelkasten can be thought of as like a wiki: each note is a page, and keywords are linked to other pages.

Why?

As I see it, there are two reasons why this idea is so useful.

Discoverability

Suppose I am writing a note about ElGamal encryption. Such a note will surely refer to other ideas on which the method is based, such as the discrete logarithm, the Diffie-Hellman key exchange protocol, and even more foundational ideas like groups. Everywhere these ideas are referenced they are linked to their corresponding notes. This is particularly valuable in the proof, where even extremely minor asides which would usually not warrant a reference to another theorem in a textbook, but are too long to include in place, can just be a link within the text that can be completely ignored if believed.

By creating links to all of these earlier ideas, other notes continue to receive attention, leading to updates and improvements.

When I am looking for something directly, I have a folder full of text files to search by name or content in whatever software I find is most appropriate.

My Zettelkasten for my mathematics notes currently contains 284,491 words over 1613 notes. It covers a variety of different subject areas, and was written over two and a half years. This way of taking notes, which allows new ideas to be collected in the same bucket, and forces the revisiting of previous work, is the only reason I can still find things after all this time.

Reusability

When you write notes digitally in a filesystem, the natural thing to do is to organise it them folders according to some notion of categorisation. Doing this in a collection of notes which you anticipate will be useful many years in the future is destined to fail, with many notes not fitting into clear mutually exclusive categories, and ideas of what are the "right" categories changing like the weather.

If I study from one book about algebraic number theory, and then from another about algebraic geometry, inevitably there are going to be points of overlap. The solution to this in Zettelkasten is to think not in terms of folders but instead in terms of contents pages. That is, there is a note about algebraic number theory which itself is just a list of links to other notes. This means folders can overlap by containing common notes.

This also makes them cheap to create. I can have a contents page for each book that I read, each University subject I have studied, and pages for different topics or paths through learning particular material. Discoverability of contents pages is then solved by a contents page of contents pages, which acts like a home page.

Another benefit of doing away with folders is that all of your notes can sit in one folder in the filesystem, thus allowing the filesystem to enforce uniqueness of the names of your notes, which helps with linking.

How?

For me, Obsidian was my entry point into creating a Zettelkasten and is still my recommendation for doing so, even though I no longer use it myself. It's flexible, whilst reliably doing the core things a Zettelkasten needs to do, and it allows you to keep all of your notes as plain text files which can be searched or manipulated with other software.

There are many other choices, zk, Logseq, Zettlr, and Notion, just to name a few.

As for me, I am currently in the process of migrating my notes over to a new format and my own app, designed around my particular desires. Yes, I do appreciate the irony of me now mentioning that I am building my own app, given my criticism of people focusing on the system of their notes rather than the content. I do however mention this for completeness and transparency given that my recommended app above is an app that I no longer use.

Now that you have read this blog post, it is time to stop sitting around thinking about how you will be productive by consuming the work of others, and actually start writing some notes. Embrace imperfection, and let the content drive the process.