Ninety thousand notes: Niklas Luhmann's second brain
Sociologist Luhmann wrote over 70 books — and credited his card file. What the famous Zettelkasten says about a company's memory.
The German sociologist Niklas Luhmann wrote more than 70 books and hundreds of academic papers in his lifetime — a level of productivity that makes no sense until you see his card file. The Zettelkasten: over 90,000 handwritten notes connected by references. Luhmann didn't speak of it as an archive but as a “communication partner” — he claimed it wasn't him writing, but the conversation between him and the card file.
Why it worked
Two principles. First: one idea, one note — small units can be combined. Second, and mainly: connection. Every note referenced others, so an old note was never buried in a drawer — it resurfaced whenever it related to something new. The card file didn't just have memory. It had the ability to speak up at the right moment. The whole “second brain” movement and tools like Obsidian or Roam stand on the same principle today.
Your company has a Zettelkasten too. Usually scattered
Now look at your company's memory: a piece in emails, a piece in heads, a piece in notebooks, a piece in Excel. The individual notes exist — the connections are missing. A note from a 2023 meeting doesn't resurface when the same customer calls in 2026; it sits in the archive of someone who no longer works there. A scattered Zettelkasten isn't memory. It's a landfill.
A note = an event on the relationship timeline
Luhmann's principle translated into sales: the unit is one event (a call, a promise, a change) and the connection is the customer — everything about them on one timeline, in the order it happened. And the main thing Luhmann knew applies: a note's value grows with time. “They're considering a second production hall” is a detail today. In two years, when they call about expanding, it's a head start the competition doesn't have.
What to take away
You don't have to write books. Luhmann's question after every meeting is enough: did I write this down so it will resurface on its own when it's needed? If not, you don't have a second brain. You have a second set of worries.
The relationship timeline in Lemnio is a Zettelkasten for customers — the notes connect themselves. Try it free, or write to [email protected].