A fleeting note is a quick capture of a thought you do not want to lose: an idea in the shower, a line that struck you mid-article, a connection that surfaced on a walk. It is written fast and meant to be temporary. The term comes from Sönke Ahrens' How to Take Smart Notes, his account of the Zettelkasten method that Niklas Luhmann used.
The point of a fleeting note is not to keep it. It is to hold a thought just long enough to decide whether it is worth keeping.
Three kinds of note, one workflow
Ahrens splits notes into three types, and confusing them is the most common mistake:
- Fleeting notes catch raw thoughts. Messy, fast, disposable.
- Literature notes are what you write while reading, in your own words, with the source attached. Brief, and kept.
- Permanent notes are finished ideas, each self-contained and written as if for someone else. These earn a place in your slip-box. See atomic notes for what a good one looks like.
The workflow runs one way. A fleeting note is reviewed soon after it is made, then either rewritten as a permanent note or thrown away. Nothing stays fleeting.
The one rule that makes them work
Process them within a day or two. This is the discipline everything else hinges on.
A fleeting note you never revisit is not a note, it is litter. The danger of frictionless capture, the reason so many apps fill with thousands of orphaned scraps, is that capturing feels like progress while changing nothing. Ahrens is blunt about it: fleeting notes only have value inside a workflow that turns them into something permanent.
So keep one inbox for them and empty it on a schedule. When you process a fleeting note, you are really asking a single question: is there an idea here worth rewriting in my own words? If yes, it graduates, ideally through the same "explain it plainly" move behind the Feynman Technique. If no, delete it without guilt. Most fleeting notes should die, and that is the system working, not failing.
Where they sit in a second brain
Fleeting notes are the front door of a second brain: the fast, low-effort layer that makes sure a good thought survives the ten minutes after you have it. But a front door is not a house. Their whole job is to feed the slower, more durable notes behind them. Build both the capture habit and the processing habit, and the rest of personal knowledge management has something real to work with. Capture without processing is just a bigger pile.