How I Decide What's Worth Writing Down

This note card from Marcus Aurelius was worth keeping.

There's a note-taking problem that nobody talks about.

It's not that people don't take notes. Most of us take too many. We highlight. We screenshot. We copy-paste entire articles into Notion folders we'll never open again. We dog-ear pages and stick Post-it notes to things and then wonder, six months later, why none of it ever turned into anything.

I've been thinking about this a lot lately, because I've watched smart, creative people build beautiful note-taking systems. Gorgeous Obsidian vaults, color-coded Notion databases, perfectly organized Readwise libraries, all functioning, in practice, as very elegant graveyards. Full of ideas. None of them alive.

The system isn't the problem. The filter is.

The Highlighting Trap

Here's what most of us do when we read something interesting: we highlight it.

And highlighting feels productive. It feels like engagement. You're interacting with the text, marking what matters, proving to yourself that you're paying attention.

But here's what highlighting actually is: it's the intellectual equivalent of taking a photograph of a painting instead of looking at it. You now possess a copy of the thing. You do not possess the thing.

Cognitive scientist John Dunlosky's landmark review of learning techniques ranked highlighting and rereading among the least effective strategies for retention, not because they're passive in the lazy sense, but because they create what researchers call an illusion of competence. The highlighted text looks familiar. Familiarity feels like understanding. It isn't. Meanwhile, Mueller and Oppenheimer's widely-cited 2014 study found that note-takers who processed and paraphrased ideas in their own words significantly outperformed those who transcribed or marked them verbatim, even when the transcribers had "more" of the material in front of them.

The brain remembers what it has to work for. Highlighting asks nothing of it.

In other words, you have to earn the learning.

Highlighting is off-loading without processing. You've marked the idea. You haven't touched it.

I spent years doing this. My books are full of underlines that I have no memory of making. My old Evernote account is a museum of things I found interesting and immediately forgot.

The shift came when I stopped asking is this interesting? and started asking a different question entirely.

The Question That Changed Everything

When I'm reading now, I ask myself one thing before I reach for a note card:

Would I want to find this in two years?

Not "is this cool right now." Not "does this feel important." Those feelings are cheap and they pass quickly. The question is whether this idea will still matter to the future version of me who is in the middle of building something, a book, an argument, an article, a project I haven't thought of yet.

It's a small shift, but it changes everything about how you read.

It moves you from passive reception to active conversation. You're no longer a tourist moving through someone else's ideas. You're a builder, scouting for materials.

When I was deep in my research on Duke Ellington's publicity manuals, I wasn't highlighting everything that seemed interesting about Ellington. I was asking: which of these details will matter when I'm trying to construct an argument? Which of these is a brick, and which is just scenery?

The scenery stays in the book. The bricks go on note cards.

Three Things Worth Capturing

Once you have the right question, the filter becomes surprisingly clear. In my experience, almost everything worth writing down falls into one of three categories.

1. Ideas that challenge something you already believe.

These are the most valuable and the easiest to miss, because they create friction. They're uncomfortable. The temptation is to skim past them, or to note them in a way that defangs them — "interesting counterpoint" — and move on.

Don't. These are the notes that will change your thinking. Write them down exactly as they hit you, uncomfortable and all. The discomfort is the signal.

2. Specific details that make abstract ideas concrete.

The name. The date. The exact number. The “name of the dog.” The anecdote that perfectly illustrates the principle.

Abstract ideas are slippery. You think you understand them, and then you sit down to write and find you can't explain them to anyone. Specific details are the anchor. They're what you reach for when the abstraction starts to float away.

When I found that early Ellington publicity manual describing his music as "primitive” and then tracked how that word was quietly changed in later versions through the decades, that specific detail became the spine of an entire argument. Abstract claims about race and representation in American music became grounded in a single word and its disappearance.

Details do that. Collect them.

3. Moments when two unrelated things suddenly connect.

I call these connection notes, and I don't make them nearly as often as I should. They happen in a flash. You're reading about one thing and something from a completely different context lights up in your mind. This is related to that. You're not sure how yet, but the connection feels real.

Write it down immediately. These moments are the raw material of original thinking. They're what happens when your accumulated reading starts to talk to itself.

What You Let Go

This is the part nobody wants to hear, but it might be the most important: most of what you read, you should not write down.

Summaries of things you already understand: let them go. Plot recaps of books you just read: let them go. Information you can Google in thirty seconds anytime you need it: let it go. General impressions that don't connect to anything you're building: let them go.

Capturing everything isn't diligence. It's avoidance. It's a way of feeling productive without doing the harder work of deciding what actually matters.

The constraint is the point. When you force yourself to be selective, what you do capture becomes more valuable to your future self, and to your thinking. Every note card I write represents a small act of judgment. This matters. This is worth the card.

That judgment, practiced over time, is what separates a graveyard from fertile soil.

A Note on Permission

I want to give you something that took me a long time to give myself: permission to let go of things that seem important in the moment.

You don't have to capture everything. You're not going to miss the idea of your life because you didn't highlight a paragraph. If something is truly important to you, it will find a way to resurface. And if you've built a good filter, the things you do capture will be worth far more than any quantity of indiscriminate notes.

Read actively. Ask the right question. Write down what's worth keeping. Let the rest stay in the book.

Your future self — the one sorting through note cards looking for the next thing to build — will thank you.

Once you know what's worth capturing, the next question is where to put it and how to use it. That's what my note card system is designed to solve — and I've written about it in detail here.

What's one idea you've read recently that you almost let slide past? Go write it down on a card. See what it connects to.