TL;DR

I spent way too long trying to fit encyclopedic notes into my Zettelkasten. The “second brain” term confused me: I thought it would be a complete extension of my memory, when in reality it’s something entirely different. Long-term memory was always my weak spot, so how was I supposed to describe encyclopedic topics in atomic notes?

The answer is simple: I wasn’t going to. That kind of knowledge doesn’t belong there.

The real value of the method comes when you use the Zettelkasten as a workspace for working through your thoughts — not as a hard drive for storing them. You don’t note what a Markov chain is; you explore why it’s relevant, which of its characteristics connect to other concepts, and how it changes your understanding of something broader.

The slip box

I have a problem with long-term memory. Always have. So when I discovered the concept of a “second brain” as a second brain to compensate for the limitations of the first, I thought: this is it.

But then you start reading about it and soon comes the concept of “permanent notes” and the idea that a permanent note should be independent, contain only one concept, and be declarative. So there I was, in the middle of a postgraduate degree in artificial intelligence and machine learning, trying to imagine how I’d write atomic notes about Markov chains. It’s a technical concept… with precise mathematical definitions… how could I turn that into a permanent note? Or would it be a literature note? Or several interlinked permanent notes? Literature notes can be considered disposable… So what? Is my knowledge about Markov chains just going to disappear?

I spent weeks trying to apply the Zettelkasten framework to various different topics. Trying to fit direct, technical information into my “second brain.” The first brain has no trouble learning certain things… why would the second one struggle?

The answer came while I was processing the literature notes I’d taken from reading “How to Take Smart Notes” by Sönke Ahrens: it doesn’t fit. And it doesn’t need to. That’s not the point.

What a “Second Brain” Really Is (and Isn’t)

Here’s the problem: the term “second brain” implies storage. A brain also stores information. If you have a second brain, it should store more information, right? After all, processing thoughts is a job exclusive to the brain.

Nope.

The real value of the technique comes from offloading your thinking. Externalizing concepts and writing them down forces you to confront them physically. It’s almost like a rubber duck that remembers what you’ve already said and, depending on the software you use, connects the conversations to each other. Luhmann argued:

Writing is not archiving what we think; it is the medium through which thinking happens. Only by externalizing an idea can we distance ourselves from it enough to judge it critically.

This changes the interpretation of the framework: it’s not your brain’s long-term hard drive but the RAM/cache where the actual processing happens.

Storage vs. Processing

The confusion is understandable. Personal productivity is a huge market, and “second brain” is a powerful, catchy term for selling books and courses.

Tiago Forte, with his PARA method, popularized the idea of a system that organizes notes, documents, ideas, and references. But PARA (Projects, Areas, Resources, Archives) is essentially a variation of David Allen’s GTD and mainly helps with organization and productivity. Useful? Absolutely. But it doesn’t have the same purpose as Zettelkasten. In “How to Take Smart Notes,” the author argues in chapter 9.5 that the GTD method is great for freelancers but not so much for intellectual or academic work. In my view, this happens precisely because of the difference in the final objective of the methods.

The Zettelkasten has a different purpose. A permanent note doesn’t exist to store information; it exists to serve a purpose in developing your thinking. Storing information is just the side effect. The permanent note is distilled knowledge. Not copied, not transcribed, but transformed during the process of elaboration in your own mind.

Back to Markov chains: I don’t need to put them in the Zettelkasten because I’m not developing any thought about them. They’re a technical fact. I can always look them up when I need to. The Zettelkasten is for when I want to explore, say, how the concept of states in Markov chains relates to the idea of atomic habits… that connection becomes a permanent note. Not the mathematical definition, but the relationship I discovered between two concepts.

Active vs. Passive Reinforcement

When you get down to it, the difference between using the Zettelkasten well and using it poorly boils down to this: active reinforcement versus passive reinforcement.

  • Passive reinforcement: You put something in the system to retrieve later. The value is in retrieval.
  • Active reinforcement: You put something in the system to transform now. The value is in transformation.

If you’re using your Zettelkasten primarily to retrieve information you’d have trouble remembering, you’re in passive mode. The Zettelkasten doesn’t compensate for bad memory — it creates an environment where memory is less relevant because you’re thinking on paper, not trying to remember.

“Second brain” sounds like a superpower: finally, a solution for our fragile memory, our information overload. But that promise is misleading.

Conclusion

Discovering that the Zettelkasten is a workspace, not a storage, changed my relationship with the method. Today, when I open my Obsidian, I don’t ask “what do I need to store?” but rather “what do I need to think about?”. Before noting something, I ask myself: what will I use this for? If the answer is “to remember later,” it’s not a permanent note. If it’s “to develop an idea,” then yes.

And Markov chains? They stay where they belong: in a statistics textbook, consulted when needed. My Zettelkasten is for more interesting things: connections, arguments, ideas in development. It’s living thought.