Zettelkasten method

The Zettelkasten (German for “slip box”) is a note-taking practice, not an app. Luhmann’s paper slip boxes worked because every slip carried one idea and the connections between slips carried the argument — the index was a by-product, never the point.

Three properties matter:

• Each note states exactly one idea, so it can be linked from anywhere.
• Links are written at the moment of writing, when the reason for the link is still known.
• Notes are addressed by a stable identifier, so a thought can be rewritten in place without breaking the links pointing at it.

The unit of thought is therefore the note, not the document. Atomic notes exist to be reused; Evergreen notes exist to be revised.

What a tool has to preserve is the link itself. Folders and tags are lossy projections of the same thing, and both rot: a note filed in one folder is invisible from every other context that would have justified reading it.