Zettelkasten
Zettelkasten is a knowledge management technique. In Zettelkasten, individual pieces of knowledge are stored on index cards. Each card includes links to other cards. Along its basic definition, Zettelkasten is a form of hypertext on paper.
The database structure of Zettelkasten is very simple, and the power of Zettelkasten comes from the way it is used. For users of SuperMemo, this mode can be compared to "incremental reading on paper". The main differences are: (1) no spaced repetition, (2) recommended constraints on the size and formulation of notes, and (3) application similar to incremental writing.
As much as incremental reading, Zettelkasten can be a very powerful technique if used skillfully.
Described by Niklas Luhmann (1927-1998), Zettelkasten was used as a powerful knowledge management system employed in prolific creative writing. In the paper variant, each card had to be meticulously crafted and classified in the system. Luhmann would engage in a "conversation with the system", in which cards would be uncovered and card links followed in search for creative inspiration. This made it possible to form a semantic network, which would be stored in the system and partly in author's memory (by virtue of semantic processing). Even though learning was not the primary purpose of Zettelkasten, the advantages of the technique as described by Luhmann are very similar to those of incremental reading (see: Advantages of incremental reading). In particular, Zettelkasten would capitalize on surprisal (for the sake of the association of ideas), forgetting (for the sake of generalization), and rich knowledge with compound benefits increasing in proportion to the size of the knowledge and its dense connectivity. The efficiency of the system is based on the power of semantic review, of which, neural creativity is a good analogy.
Similarities of Zettelkasten to incremental reading can best be shown by parallel correspondence of their basic ingredients. "Card ID" is an equivalent of the element number, which is not of much use in incremental reading due to its digital implementation. "Card content" can be seen as an element's content in the form of text. A "literature note" (highlight) is little else than an extract (in Zettelkasten it is made manually in one's own words). In SuperMemo, the role of "Related notes", which link individual cards/elements, is played by links, hyperlinks, concept links, knowledge tree relationships, tags, and more.
Applications that aim at implementing the power of Zettelkasten can be seen as independently evolving branches of software that will ultimately converge on some kind of universal incremental reading. One of the first steps in that direction would be the adoption of spaced repetition.
Zettelkasten can also evolve in the direction of a personal wiki. As most of the materials for SuperMemo Guru are born in incremental writing in SuperMemo, this wiki can be seen as another metaphor for the method.
See also: Zettelkasten in 4 min
This glossary entry is used to explain SuperMemo, a pioneer of spaced repetition software since 1987