u/zleonska in discussing their paper notebook commonplace practice reports that finding their material within multiple notebooks isn't difficult but that, like W. Ross Ashby, they use index cards to index their commonplaces.

Journal of W. Ross Ashby

reply to: https://www.reddit.com/r/antinet/comments/wvn38a/using_notebooks_with_your_antinet/

Ross Ashby, a systems theorist like Luhmann, had a sophisticated hybrid notebook/index card system that some here might find an interesting and usable model, particularly if they're enamored of the notebook format. It's been digitized and is online for perusal: http://www.rossashby.info/

https://niklas-luhmann-archiv.de/bestand/zettelkasten/zettel/ZK_2_SW1_001_V

One may notice that Niklas Luhmann's index within his zettelkasten is fantastically sparce. By this we might look at the index entry for "system" which links to only one card. For someone who spent a large portion of his life researching systems theory, this may seem fantastically bizarre.

However, it's not as as odd as one may think given the structure of his particular zettelkasten. The single reference gives an initial foothold into his slip box where shuffling through cards beyond that idea will reveal a number of cards closely related to the topic which subsequently follow it. Regular use and work with the system would have allowed Luhmann better memory with respect to its contents and the searching through threads of thought would have potentially sparked new ideas and threads. Thus he didn't need to spend the time and effort to highly index each individual card, he just needed a starting place and could follow the links from there. This tends to minimize the indexing work he needed to do regularly, but simultaneously makes it harder for the modern person who may wish to read or consult those notes.

Some of the difference here is the idea of top-down versus bottom-up construction. While thousands of his cards may have been tagged as "systems" or "systems theory", over time and with increased scale they would have become nearly useless as a construct. Instead, one may consider increasing levels of sub-topics, but these too may be generally useless with respect to (manual) search, so the better option is to only look at the smallest level of link (and/or their titles) which is only likely to link to 3-4 other locations outside of the card just before it. This greater specificity scales better over time on the part of the individual user who is broadly familiar with the system.

Alternatively, for those in shared digital spaces who may maintain public facing (potentially shared) notes (zettelkasten), such sparse indices may not be as functional for the readers of such notes. New readers entering such material generally without context, will feel lost or befuddled that they may need to read hundreds of cards to find and explore the sorts of ideas they're actively looking for. In these cases, more extensive indices, digital search, and improved user interfaces may be required to help new readers find their way into the corpus of another's notes.

Another related idea to that of digital, public, shared notes, is shared taxonomies. What sorts of word or words would one want to search for broadly to find the appropriate places? Certainly widely used systems like the Dewey Decimal System or the Universal Decimal Classification may be helpful for broadly crosslinking across systems, but this will take an additional level of work on the individual publishers.

Is or isn't it worthwhile to do this in practice? Is this make-work? Perhaps not in analog spaces, but what about the affordances in digital spaces which are generally more easily searched as a corpus.

As an experiment, attempt to explore Luhmann's Zettelkasten via an entryway into the index. Compare and contrast this with Andy Matuschak's notes which have some clever cross linking UI at the bottoms of the notes, but which are missing simple search functionality and have no tagging/indexing at all. Similarly look at W. Ross Ashby's system (both analog and digitized) and explore the different affordances of these two which are separately designed structures---the analog by Ashby himself, but the digital one by an institution after his death.

Sorry, just seeing this now. It's assuredly a sliderule, which would have been a common tool for engineers and mathematicians of his era to have had. They became less common with the advent and proliferation of calculators.

For those interested in looking at a system in English but with a slightly different form, but ostensibly similar, try W. Ross Ashby's digitized note collection: http://www.rossashby.info/

Perhaps not coincidentally, Ashby was a research colleague of Luhmann's.