How to Build a Second Brain: Journaling, Digital Gardens, and the Art of Lifelong Learning

Why Build A Second Brain

There was a time in my life when the stack of unread books on my nightstand gave me terrors. Luckily, now I have audiobook subscriptions and bookmarked ebooks and I can’t see them looming over me all the time to give me the shivers.

It’s a well-established fact that our memory can hold only three or four items at a time, so it’s a good idea to offload our ideas onto a second brain aka a notebook. I wrote about my own collection-book mechanism a while ago in How to Extend Your Brain.

Over the past decade, I’ve mostly shifted my note-filing system online. I still take handwritten notes daily, but I file them in OneNote periodically. It’s my go-to place for brain dumps, where I can organize and search for ideas as I write about a specific topic.

I keep my calendar, to-do lists, and drafts all in one place, synced across devices at any point in time. As I researched other ways to stay organized and efficient, especially around this idea of the digital garden, I realized there are many different approaches, and no single right way to do it.

For me personally, a notebook, whether online or in my hand, is the best way to stay present in the moment, without worrying that a passing idea will disappear forever.

Journaling That Sustains

My OneNote has two sections.

One is operational: messy, impromptu, needs filing, and very much on the go. I’ve made peace with the fact that this part will never be tidy.

The other is strategic, meant for long-term project ideas and plans. This is where ideas are allowed to mature.

There was a time I went through a decade-long phase of sticky notes and index cards, winding myself into knots arranging and rearranging them LOL.

Now, I let the operational notebook stay imperfect.

Otherwise, I’d drive myself crazy pruning it to perfection, and that’s not sustainable. Just imagining my former self as an inbox-zero hero, obsessively emptying my inbox every night, still gives me shudders.

My One Note

Different Knowledge Management Systems 

For a while now, thanks to the German sociologist Niklas Luhmann, we’ve had the Zettelkasten system of collecting and connecting notes. He used interconnected note slips (Zettel) to achieve extraordinary academic productivity, publishing over 50 books and hundreds of articles in his lifetime.

The idea is simple. Each note is a small idea-atom, filed alongside related ideas, slowly building depth and connection over time.

Then came the Memex, proposed by Vannevar Bush, essentially a machine version of the Zettel. The goal was to make stored information mimic how the mind works, associating ideas freely if everything were available at once. Today, we have many apps that claim to help consolidate our notes and bookmarks and prune them for us.

Still, my favorite evolution of all these systems is the idea of the digital garden. Nothing is ever fully “done,” and that feels deeply human. That philosophy is what finally helped me make peace with my operational notes dump.

If you want to be present, to think deeply and creatively, extend your brain with systems like these. Whatever knowledge management approach you adopt, the right one will liberate you.

So whether you’re seeking structure, linkage, or growth in knowledge, there’s a system for you. You can use one or a combination of these ideas — OneNote, Zettelkasten, Memex, Digital Gardens.

The real test is simple: Does it help you keep what you learn close enough to shape who you’re becoming?

A Memex Machine of 1945 by Vannevar Bush

The Memex Animation – Vannevar Bush’s Diagrams Made Real

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