glossary / zettelkasten
Zettelkasten
A Zettelkasten is a note system of small, single-idea notes, each with a fixed address, connected by explicit links rather than filed under topics.
Zettelkasten is German for “slip box”: a collection of small notes, one idea each, that are linked to one another instead of being sorted into categories. The method is defined by three rules: notes are atomic, every note has a permanent address, and connections are written into the notes as references.
Origin
Card files for research go back centuries; Wikipedia traces them through Conrad Gessner, Leibniz and Linnaeus (Wikipedia: Zettelkasten). The modern method comes from the sociologist Niklas Luhmann, who built a box of roughly 90,000 cards between the 1950s and his death in 1998 and credited it for some 50 books and 550 articles. His 1981 essay Kommunikation mit Zettelkästen describes the design decision that matters: notes are not ordered by topic but by fixed position. Each card gets a number that never changes; a new card can be inserted behind any existing one (57/12 is followed by 57/12a, then 57/12a1), and any card can cite any other by number. A keyword register is the entry point, since there is no table of contents. Luhmann argues that a note without links “will get lost in the Zettelkasten” (English translation at zettelkasten.de).
How it works on a computer
Software makes the fixed address trivial: a filename or a timestamp id is permanent enough, and [[wikilinks]] replace hand-copied numbers. Backlinks give the reverse direction that Luhmann had to maintain by hand. The discipline that remains is the writing: one idea per note, in your own words, with the link and a sentence saying why it is relevant.
Pitfalls
The method rewards linking and punishes filing. Deep folder trees recreate the topic hierarchy Luhmann rejected. Timestamp ids (202609221430) are unambiguous but unreadable as link text, which is why most Markdown tools resolve links by title instead. Collecting is not the work; a large box of unlinked quotes is a scrapbook, not a Zettelkasten.
In other tools
Obsidian and Foam are general-purpose and fit the method through wikilinks and backlinks. Zettlr lists Zettelkasten support as a headline feature and has a dedicated link-management module (Zettlr README); The Archive, from the zettelkasten.de authors, is a plain-text macOS app built around it (The Archive). Any folder of Markdown files with title-based links is enough; the software matters less than the two habits of splitting and linking.
In tnotes
tnotes does not generate ids and has no Zettelkasten mode; it provides the primitives. Each note is a Markdown file whose title is its address: [[Title]] links resolve by title, alt+enter follows one, and a missing target is created on the spot, so a link written while thinking becomes the next note. The backlinks overlay and the backlinks field in ls --json give the reverse direction. Renaming a note rewrites every link to it, so titles can change without breaking the box.
tnotes new "Attention is a bottleneck" --tag zk
tnotes ls --tag zk --json | jq '.[] | {title, links, backlinks}'Folders are ordinary directories and optional. See /for/zettelkasten and /compare/tnotes-vs-zettlr.