I recently discovered something truly valuable. I read — and reread — a remarkable book: The Notebook by Roland Allen, published in 2023. Since then, I’ve given away piles of copies to anyone I think must read it. The book is a historical reconstruction of how humans started writing things down. And it turns out to be far more important and impactful than we’ve ever realized. It lays the historical foundation for PKM: Personal Knowledge Management.

One of the most groundbreaking insights I took from it was that before the printing press and before the Renaissance, something else happened that paved the way for both. In a small village outside Florence, someone discovered how to produce paper from wood pulp and linen—much cheaper and faster than before. Until then, people mostly wrote on parchment, which required a lot of leather, hide, and urine. Not exactly accessible in terms of price or availability. What followed was an explosion in access to paper, and people began using it in every way imaginable—and of course, also misusing it. And once people start writing down lots of things, it’s only a matter of time before someone begins thinking about how to structure and organize all that information effectively.

That’s how the so-called double-entry ledger was born. Anti-capitalists might call it the root of all evil, but The Medici of Florence could never have built their empire without it. This system for tracking money flows and loans — using debit and credit — became the cornerstone of early capitalist success. Riding that wave, people like Da Vinci and Michelangelo suddenly learned how to capture their thoughts and ideas in smart, structured ways. And in Italy at that time, the famous zibaldones emerged: various types of notebooks, each with its own purpose, used to capture personal ideas, reflections, observations, and knowledge. A paper-based PKM system!

This made it possible for someone like Geoffrey Chaucer — best known for The Canterbury Tales — to become one of the most enthusiastic promoters of such practical notebooks. This helped spark early industrial developments in England. Philosopher John Locke even wrote his own version of what we’d now call Building a Second Brain or Linking Your Thinking: A New Method of Making Commonplace Books.

All of this led, on one hand, to the works of Isaac Newton, Charles Darwin, Alexander von Humboldt, and Linnaeus (who invented the famous index cards), and on the other, to the invention of the vischboeck in the Netherlands. I had never realized that.

There was a time when people didn’t even have shared names for fish. Not ideal if you want to record, preserve, study, or trade them. In the days of parchment, this simply didn’t happen. A fish in Scheveningen had a completely different name than the same fish in Harlingen.

This knowledge eventually became the foundation of the Dutch East India Company’s massive success. Global trade in money and goods depends on clear agreements — and on the ability to document them properly.

This book, then, touches on a lineage thousands of years old — how humans write, why they do it, and in what ways. A fun detail is that it includes a full chapter on how police officers are trained to record things properly in their notebooks — without the possibility of altering the evidence later (to prevent corruption). To this day, this remains a challenge: how do you train law enforcement to reliably record personal observations and knowledge?

You could say the first wave of PKM began with the invention of paper and these special notebooks — the zibaldones and commonplace books. The second wave arrived with the rise of the personal computer and later the smartphone. This sparked a new interest in capturing personal data. David Allen created the GTD method, Merlin Mann gave us the Hipster PDA and 43 Folders, and Ryder Carroll — extensively featured in Allen’s book — introduced the famous Bullet Journal.

Now, in 2025, it’s safe to say we’re at the dawn of a third wave. With growing awareness of PKM and the rise of the term itself — and with thinkers like Nick Milo, Anne-Laure Le Cunff, Nicole van der Hoeven, Tiago Forte  and Zsolt Viczián— we’re entering a new phase in understanding how to manage personal information.

I’ve long suspected that my own personal ontology was a more essential piece of the puzzle than I realized. After reading this book, I’m sure of it. Irrational databases rock! So does linked thinking — far beyond the dogma of “the document.”

In large organizations, this topic is still being ignored. They prefer to struggle with big, complex systems that are neither intuitive nor cost-effective. But if you don’t empower individual employees to manage their own information and knowledge — a basic requirement for being valuable in their daily work — then you’re left with frustration, delays, and unnecessary limitations. No wonder freelancers and small startups move much faster. They take their tools, knowledge, and information dead seriously.

What we’re doing with the Digital Fitness Community and the annual PKM Summit is not a niche. I believe it’s one of the most foundational developments in the history of information. I’m confident it will be widely recognized within the next ten years. People with solid digital hygiene and skills will be the first to benefit. All the knowledge, insights, and ideas around this are flowing to and through the Digital Fitness Community. So if you, like me, sense something beautiful is emerging — stay close!

And read that book.