In practice, quite a few people ask about the difference between reference notes and permanent notes. The distinction relies heavily on tacit knowledge, so it's tricky to answer. If I answer based on my own context, it sometimes won't fit someone else's. Still, I'm writing this to explain it as best I can.
In Sönke Ahrens's Zettelkasten, notes are broadly sorted into three kinds: fleeting notes, literature notes, and permanent notes. But you could really say there are only two: literature notes and permanent notes1. Fleeting notes simply catch a thought so it doesn't evaporate. 2
Before answering, here are a few principles worth knowing.
- A natural classification is better than a rigid one.
- When writing a note, ask yourself: "When will I be looking for this note?"
Distinguishing Reference Notes from Permanent Notes
First, the Zettelkasten came out of academia. When writing a paper, you often need to cite references. Also, in academia, the main job itself is reading papers and thinking. So it's natural to write down the thoughts you have after reading a paper, just as we wrote book reports after reading books. Reference notes become necessary against this background.
Is the difference how polished the writing is?
No. What matters more than polish is where the note started from. If the thought came up while reading some material, you don't need to worry about what a permanent note is. You just write it down as a reference note first. That said, if the source of the material doesn't really matter, you can simply write it as a permanent note. That applies if, unlike with a paper, you won't need to cite references one by one, or you won't need to find that material again.
If a reference note also summarizes things in my own words and adds my own thoughts, how is it different from a permanent note?
The content of a reference note you write while engaging with material can connect to your existing thoughts. Then, later, a permanent note can cite that reference note.
Also, a reference note doesn't necessarily have to summarize in your own words and add your thoughts. As I went along, I found that sometimes it's better to just copy and paste the original text, because when you cite that part later, you don't need to look the material up again. Just don't paste mindlessly until it evaporates from your memory and you can't make use of it. That's about all you need to keep in mind.
Should a literature note hold only what I understood from the book, with derived thoughts going into permanent notes and the two linked together?
Yes. As you try to do it that way as much as possible, you'll get a feel for which derived thoughts end up in reference notes and which in permanent notes. It isn't only a matter of what kind of thought it is; I think computer skills play a part too. If creating and linking new notes isn't smooth, you'll find linking permanent notes a hassle and stop doing it.
Writing Reference Notes
Should I store multiple thoughts about one source in a single reference note, or split them up?
Another principle of mine is "when you're torn about whether to split, don't." On paper, the margins might force a split. Where possible, writing it all in one note will be more convenient. In any case, a permanent note can link to a specific part of a reference note with a block link.
What do I record in a reference note?
The answer may sound strange, but you just record "what strikes you." Write down what you think you'll use later, or what seems to resonate with you.
If you want to quote the original as is, you can simply copy and paste it.
You can also write something down if it matches or contradicts your existing thinking, or if you learned something new that you feel you must remember.
If you try to write too much, it becomes exhausting, and you either stop writing or rarely look at your reference notes. If you write too little, you may not be able to use them when it counts. So you have to find the balance between the two yourself.
Writing Permanent Notes
Can I understand a permanent note as a paragraph with a single central sentence?
Writing it that way is fine. But how you define a paragraph varies from person to person. In a field I don't know well, I can't see the details, and the whole looks like a single thing. It's like how foreigners see East Asians as simply Chinese or Japanese, or how we Koreans don't distinguish the countries of the African continent in detail and see them as one.
In a field you know well, you can see the details, so you get a feeling of "this is different" and naturally separate things. To return to what I said earlier: when you're torn about whether to split, don't. Later, a feeling will come that says, "ah, this one needs to be split."
Also, in my personal experience, a note that started out as about one paragraph sometimes grows into a huge note....
When a derived thought comes up while writing a permanent note, do I split it into another permanent note file instead of continuing in the same one?
Continuing from the answer above: as you come to know more, the details naturally become visible, and you may get a feeling of "this is different" that you didn't have before. That's when you split it off into a separate permanent note.