Main idea

The word "atomic" suggests a minimal unit, and pushes you to believe a good note is as short as possible. The criterion lies elsewhere: a note is atomic when everything it contains serves the same conceptual center of gravity.

A note can therefore run three lines or fill a page, hold a definition, an explanation, an example and a caveat, and stay atomic if those four elements illuminate the same idea. Conversely, two sentences are enough to break atomicity: "atomic notes help you write faster" and "they also help you organize your sources better" look alike, but one is about writing and the other about organizing knowledge — they deserve two notes.

So the test to apply is not "is it short enough?" but "does everything serve the same idea?". The two questions contradict each other regularly, and it is the second that settles it.

Why it matters

It changes what you fix when a note is not working. Under the length criterion, you shorten, you cut the examples and the caveats — and you get notes that are accurate, impoverished, and no longer connectable to anything. Under the cohesion criterion, you split, which produces two complete notes instead of one amputated note.

It also defuses the most common objection to the method, the one about chopping thought into slogans: that chopping is not what atomicity asks for, it is what a misreading of the word makes people do.

Nuances and limits

Cohesion does not exempt you from every judgment about size. A note that grows almost always ends up harboring a second idea, and length remains a good alarm signal — a signal, not a criterion.

And the "same center of gravity" is observed more than it is proved: two people can judge differently whether an example serves the main idea or opens another one.

Open questions

• Is there a sign internal to a note, other than attempting to split it, that reveals it carries two centers?