I'm somebody who writes a lot—half a million words and 200 blog posts in the past 8 months. I'm also someone with an unrelenting curiosity to better understand our world. Beyond that, I also graduated with a degree in English literature with honours, with a 3.8 GPA. So, it should be no surprise I've done extensive research on how best to do research, which resulted in me diving into the world of personal knowledge management systems. These are the systems and methods of keeping track and sorting the notes we take, along with any other writing we do.

PKMs have existed for many decades (this paper is from 1999), and digital notetaking apps such as Evernote have as well. But if you know what I'm talking about, you probably associate the idea with the application Obsidian.

Obsidian has been out for six years now—has there been an increase in public-facing understanding and knowledge?

I think it's safe to say that, while there have always been courses and lessons on productivity people sell and buy, the unique values and principles of Obsidian (local plain-text files written in Markdown, data privacy, portability, "future-proofing," etc.) give the ideas and the people behind them a certain higher-brow purpose and epistemological value.

With applications like Evernote or Todoist, there has always been a more inherent focus on the nebulous concept of productivity: getting things done x10 faster and more efficiently so you have more time to get more things done. There has always been a professional business aesthetic associated where the implicit understanding is to maximize profit with the least amount of effort. Even in more personal modalities, it's about being mindful about throughput and how to increase it.

The aesthetic understanding of applications like Obsidian are different—there is a more, seemingly noble cause of pursuing knowledge and curiosity. To synthesize the endless sources of raw information and transform them into personal important wisdom to share with others.

And please don't get me wrong, I think that's a wonderful goal to pursue, I mean it is clear on my site that this is exactly what I'm dedicating my life towards.

My concern is in the lack of critical examination of what these complex, robust systems are producing: Has there been a meaningful increase of understanding and creation thanks to personal knowledge management systems? This is the question I want to investigate and try to answer.

PKM Examples

Before trying to answer that question, I want to first go over specific examples of personal knowledge management frameworks so we have an understanding of what I'm talking about, exactly.

Organization-first systems

• PARA (Tiago Forte): sorts everything into Projects, Areas, Resources, Archives, organized by actionability rather than topic.
• Johnny Decimal: a strict numeric taxonomy (10-19, 11.01, etc.) originally for file systems, now used for notes too.
• LATCH (Richard Saul Wurman): Location, Alphabet, Time, Category, Hierarchy. Less a system than a checklist of the five ways any information can be organized.

Note-linking / emergent systems

• Zettelkasten (Niklas Luhmann): atomic notes, each one idea, linked to other notes rather than filed into folders. Structure emerges from the links, not a predetermined hierarchy. Uses "Folgezettel" (sequential branching IDs) in the original paper-slip version.
• Evergreen notes (Andy Matuschak): a modern gloss on Zettelkasten: notes should be atomic, concept-oriented, densely linked, and written/rewritten over time rather than left as one-off captures.
• Maps of Content (MOCs): popularized in the Obsidian community; instead of folders, you build index notes that link out to clusters of related notes, and can have many overlapping maps.
• Digital garden: notes published in a semi-public, always-growing, non-linear state (as opposed to a polished blog post), often explicitly showing "seedling → budding → evergreen" stages of an idea.

Capture/workflow-oriented

• CODE (Tiago Forte, pairs with PARA): Capture, Organize, Distill, Express. A pipeline for turning raw input into usable output rather than a filing scheme per se.
• Progressive summarization: also Forte's. Each pass through a note, bold/highlight the most important parts, so a note gets more distilled each time you revisit it.
• GTD (David Allen): technically a task-management system, not PKM, but it's so often bolted onto PKM setups (especially with PARA) that's worth listing. Capture, clarify, organize, reflect, engage.

Older/analog roots

• Commonplace book: centuries-old practice of copying quotes, ideas, and observations into a single running book, usually with a personal indexing scheme. A direct ancestor of most digital note-linking systems.
• Card index / slip-box methods more broadly: the pre-Luhmann tradition (e.g., how many academics kept index cards) that Zettelkasten formalized.

Now that we have these frameworks established, let's attempt to tackle specific questions:

1. First, what does it mean to make an important and meaningful contribution to our understanding of the world?
2. Second, are PKM frameworks being used by those making important, meaningful contributions in fields of academia and communications? By communications, I mean synthesizing the understanding of expert-domains so these discoveries can be understood and shared among everyone instead of gatekept by elitism.
3. Third, what does the process actually look like for the actual people who write important papers and books?
4. Fourth, what is the throughput and output of the people who have dedicated themselves to PKM frameworks?

Answering these questions will help shed light and provide clarity on whether the years of courses and frameworks designed around a wonderful, free plain-text app have positively contributed to humanity, or if it is indeed just a circular cottage industry.

The Luhmann Myth

To start, a large portion of the culture surrounding PKMs originates from the methodology of German sociologist Niklas Luhmann, as he was famous for his use of the "slip box" or Zettelkasten note-taking method and the achieved output of more than 70 books and nearly 400 scholarly articles. This is the kind of remarkable output that many in the PKM community aspire towards.

Bielefeld University has been digitizing Luhmann's actual Zettelkasten since 2015, viewable at niklas-luhmann-archiv.de. It's a decades-long, publicly funded project.

In a 2022 university feature on the digitization effort, the project's scientific coordinator, sociologist Johannes Schmidt, says outright that Luhmann liked to cultivate the myth that the box—not he—produced the books, and that anyone hoping to replicate that output just by having access to the actual cards will probably be disappointed.

The Zettelkasten community has independently arrived at the same problem. One thread posed it as a direct challenge: Luhmann's catalogue is now available to everybody, so why haven't hundreds of sociologists used it to publish dozens of books?

Question 1: What counts as a meaningful contribution to understanding?

Our current understanding of cognitive science doesn't actually support the "network of linked notes generates insight" mechanism that Zettelkasten evangelists lean on.

The empirical literature on insight and creativity centers on incubation, the act of stepping away from a problem, unconscious restructuring, working memory offloading. This is not the act of browsing a hyperlinked card catalog.

There has been meta-analysis on incubation effects across creative, visual, and linguistic insight problems and research on distributed cognition and material tools in insight problem-solving which demonstrate this.

Margaret Boden's concept of combinatorial creativity, which is defined as recombining familiar elements into something surprising, is the closest existing theory to what PKM systems claim to enable, but it's a much older and more general idea than anything Obsidian or Luhmann invented, and it doesn't require or predict that note-linking specifically is the mechanism.

Ithaka S+R's 2018 issue brief "Scholars ARE Collectors" argues that collecting, hoarding, and idiosyncratically organizing personal archives are, in fact, structurally inseparable from how research actually gets done. The problem they identify isn't that scholars collect too much; it's that institutions don't support the collecting scholars are already doing.

Question 2: Are PKM frameworks used by people making real contributions, or mostly by people selling PKM?

Andy Matuschak, originator of "evergreen notes," has a note titled People who write extensively about note-writing rarely have a serious context of use. He argues most people who write advice about note-taking aren't applying their systems to a real external problem, and their actual creative output is the productivity content itself.

Matuschak contrasts how Luhmann barely wrote about his Zettelkasten and instead produced research; whereas modern PKM bloggers do the opposite. Matuschak includes himself as vulnerable to this pattern.

There's a whole subgenre of books about PKM and Zettelkasten, catalogued in this Obsidian forum thread. Ahrens, Forte, Kadavy, Scheper, and others, each producing a book whose primary subject is how to take notes, rather than a book that uses notes to say something new or useful about the world. Tiago Forte claims over 20,000 people have taken his course and 100,000+ copies of his book have sold. This is the actual documented output of the "Second Brain" movement: a course business, not a body of external work produced using the method.

Emile van Krieken is an extremely productive academic, with 2,100 papers and 900 topic notes, real research retrieval. He says he does not follow Zettelkasten/evergreen-notes orthodoxy, but instead built something bespoke to his own personal research problem. Systems work when they're subordinate to real work, not when the system itself is the project.

The academic research field known as Personal Information Management (PIM) goes back to a 2004 CHI conference, and their research on how scholars manage their information has been that they do it idiosyncratically and largely without formal branded systems, see the Emerald study on scientists' information practices and the literature review on PIM organizing/finding/keeping activities. Nobody in this research literature is measuring Zettelkasten adoption as a variable, telling of how marginal these branded systems are to how research actually gets managed.

Question 3: What does the process actually look like for people who write important books?

The analogue systems used by demonstrably prolific working writers are project-bounded and disposable. The digital PKM ideology sells the opposite promise of a permanent, ever-growing, cross-project system that gets more valuable the longer you maintain it.

Robert Greene's notecard system, as described by his former research assistant Ryan Holiday in The Notecard System and covered in this piece on trying it out, is analogue, index-card-based, and organized around a specific book's themes. This is not an ever-accumulating cross-project "second brain." Greene reportedly said a good source book generates 20–30 notecards; a bad one, two or three. The cards get filed by theme, not linked bidirectionally, and they get physically shuffled and color-coded per project.

John McPhee researches a piece exhaustively, then makes an index card per structural component of that specific piece, physically arranges and rearranges them on a table or wall, and only then writes. This system also resets with every project. There's no persistent, cross-project knowledge graph. The organizing structure is disposable, built to solve one piece's problem, then discarded.

Susan Cain dumps everything into one giant Word document; other writers use rubber-banded index cards or cut-up photocopies. The system is personal, ad hoc, and built around the specific cognitive demands of one project rather than a general-purpose "external brain" meant to serve every project forever.

Question 4: What is the actual throughput of people dedicated to PKM?

The clearest, most measurable output of the PKM movement is, simply, more PKM content and not externally-facing work. There's an ecosystem within the cottage industry. PARAZETTEL is explicit that its business is "PKM theory" as a product in itself, independent of any particular app or any particular piece of writing produced using it.

There is a false sense of accomplishment that comes with saving information, known as the "collector's fallacy". It is a dopamine-driven cognitive bias.

Estimates for the global self-improvement/personal-development market range from $41–46 billion in 2022–2025 to projections of $84–91 billion by the mid-2030s. No market researcher segments PKM out separately, but even a fraction of that is extremely lucrative.

The Generative AI Problem

I want to note something important before concluding this piece, which is that I didn't even touch on how much LLM chatbots and genAI features have been integrated into PKMs and note-taking apps. It's increasingly common to see PKM framed as "an AI-native knowledge base" instead of "a better notebook."

Part of the explosion of popularity for apps like Obsidian is not their utility for knowledge, but rather the fact that they work so well with genAI at all—as these tools work best with Markdown and plain-text, which is exactly what Obsidian offers.

It is personally horrifying to see people who will now write that "AI has largely eliminated the need for meticulous manual organization."

What was once the most human readable markup format created all the way back in 2004 has been gentrified by power-hungry hallucinatory machines. While the emerging, existential issues of genAI are certainly not unique to PKMs or note-taking apps, I did want to highlight this. I promise there is a deep debt to be paid if you attempt to offload cognitive labour to a non-deterministic machine, especially if you care about objectivity and facts.

Conclusion: What Beginners Should Do

I failed at answering the primary question I had. I couldn't find a controlled, scientific study which tracks book/paper output before and after PKM adoption. The best you get is anecdotal self-report on forums, like this Zettelkasten Forum thread literally asking users what they've produced since starting, where the honest answers trend toward "more clarity and less anxiety" rather than "more finished work."

After researching... well, research, a part of me feels a sense of relief. The fact is that I've been using ad-hoc, improvisational methods for research and knowledge management for my entire life. It's clear I haven't been missing out on deeper, richer understandings by way of more complex knowledge management systems. I've always felt the act of doing and the act of planning were funnily antithetical to one another.

It's clear that if you are somebody who already has an effective throughput, then the specifics of the underlying mechanics are uniquely personal and you should continue doing whatever works for you.

But if you're someone who's just beginning and feels overwhelmed by the amount of frameworks and systems that you find, and if you feel as though you need to spend money on a course or a book to instruct you how to take notes and learn, then I have to implore you to just start creating instead. Start a blog! Learn and freewrite on your discoveries, the organization and sorting of those notes can come later, if at all.