Once you actually start writing, quite a few people ask about the difference between reference notes and permanent notes. Drawing the line between the two involves a lot of tacit knowledge, which makes it a tricky question to answer. And since my answers tend to be shaped by my own context, they don't always fit someone else. Still, I'll try to explain it as best I can.
Sönke Ahrens's Zettelkasten divides notes into three broad types — fleeting notes, literature notes, and permanent notes — but you can really think of it as just two: literature notes and permanent notes1. Fleeting notes simply keep a thought from evaporating. 2
Before I answer, here are a couple of principles worth keeping in mind.
- Natural categories beat rigid ones.
- When you write a note, ask yourself
이 노트를 내가 언제 찾게 될 것인가?
Telling Reference Notes and Permanent Notes Apart
First, Zettelkasten came out of academia. When you're writing a paper, you have to cite references constantly. What's more, in academia the core work itself is reading papers and thinking about them. So writing down the thoughts you have while reading a paper is a natural thing to do — just as we used to read a book and then write a book report. Reference notes become necessary against that backdrop.
Is the difference how polished the writing is?
No. Where the note started matters more than how finished it is. If a thought came to you while reading a source, just put it in a reference note without agonizing over what counts as a permanent note. That said, if the source itself doesn't particularly matter, you can simply write it in a permanent note — cases where you won't need to cite references one by one the way a paper does, or where you'll never need to track that source down again.
If a reference note also involves summarizing in my own words and adding my own thoughts, how is it different from a permanent note?
The content of a reference note you wrote while going through a source may connect to thinking you already had. In that case, you can later cite that reference note from a permanent note.
Also, a reference note doesn't have to be a summary in your own words with your thoughts attached. In practice, I've found that sometimes it's better to simply copy and paste the original text, because then you won't have to go hunting for the source again when you want to quote that passage. Just keep in mind that if you copy and paste mindlessly, the material may evaporate from memory and end up unusable — that's about as far as you need to take it.
Do literature notes hold only my understanding of the book's content, with any thoughts that spin off from it going into permanent notes that link back?
Yes. Try to work that way as much as you can, and you'll gradually develop a feel for which spin-off thoughts end up in a reference note and which end up in a permanent note. I think this isn't purely about the nature of the thought — your computer skills factor in too. If creating and linking a new note isn't smooth, linking to a permanent note feels like a chore and you stop doing it.
Writing Reference Notes
Should several thoughts about one source go in a single reference note, or be split apart?
Another of my principles is: "When you're torn about whether to split, don't." Writing reference notes on paper can force a split simply because you run out of room. Otherwise, keeping it all in one note will usually be easier. In any case, you can link to a specific part of a reference note from a permanent note using a block link.
What kinds of things do you record in a reference note?
This may sound like an odd answer, but: record whatever "strikes you." Anything you think you'll put to use later, or anything that resonates.
If you feel you'll want to quote the original text verbatim, just copy and paste it.
Write it down when it matches something you already thought, when it contradicts it, or when you've learned something new that you definitely want to remember.
If you try to write down too much, it gets exhausting and you'll either stop writing or stop looking at your reference notes. Write too little and you may not be able to use them at all. So you have to find the balance in between for yourself.
Writing Permanent Notes
Should I think of a permanent note as a paragraph with a single topic sentence?
Writing them that way is perfectly fine. But how you define a paragraph varies from person to person. In a field you don't know well, the details are invisible and the whole thing looks like a single undifferentiated mass — the way foreigners see every East Asian as Chinese or Japanese, or the way we Koreans lump the countries of Africa together without distinguishing among them.
In a field you know well, the details are visible, so you'll get the sense that "this is a different thing" and split it apart naturally. To repeat what I said earlier: when you're torn about whether to break something up, don't. Later on, you'll get the feeling of "ah, this needs to be split."
Also, in my personal experience, some notes start out as roughly a single paragraph and grow into something enormous....
When a thought spins off while I'm writing a permanent note, do I keep writing in the same note or split it into another permanent note file?
This follows from the answer above. As you learn more, the details naturally come into view, and unlike before, you may get the sense that "this is a different thing." That's when you split it into a separate permanent note.