PKM systems use different note types to reflect the stage of processing and the nature of the content. Understanding this taxonomy prevents the common mistake of treating all notes equally, which leads to either over-processing quick captures or under-processing important insights.
The Three Core Types
The most influential taxonomy comes from the Zettelkasten Method, formalized by Sönke Ahrens in "How to Take Smart Notes":
Fleeting Notes
Back-of-the-napkin captures. Temporary by design. These are quick jottings meant to prevent an idea from being lost; they are not meant to be preserved permanently.
Characteristics:
- Informal, fragmentary, unpolished
- Captured in the moment with minimal friction
- No requirement for completeness or clarity
Lifecycle: Review regularly (daily or weekly). For each fleeting note, either promote it to a literature note or permanent note, or delete it. Fleeting notes that sit unprocessed for weeks are not serving their purpose.
In practice: Bullet points in Daily Notes, margin scribbles, voice memo transcripts, quick captures in a mobile app.
Literature Notes
Notes taken from external sources: books, articles, videos, podcasts, conversations, courses. They document what someone else said or wrote, ideally in your own words.
Characteristics:
- Reference a specific source
- Summarize, paraphrase, or quote key points
- Include bibliographic information
- May contain your reactions and questions, but the primary content comes from the source
Lifecycle: Literature notes persist as references. They serve as the bridge between external information and your own thinking. Over time, the insights from literature notes get extracted and integrated into permanent notes.
In practice: Book notes, article highlights with commentary, lecture summaries, podcast key takeaways.
Permanent Notes
Your own ideas, written in your own words. These are the most valuable type. They represent processed, understood, and integrated knowledge. In Zettelkasten terminology, these are the actual "Zettels."
Characteristics:
- Written entirely in your own words
- Capture one idea each (see Atomic Notes)
- Self-contained; understandable without reference to the source
- Richly linked to other permanent notes
- Titled as claims or concepts, not as topics
Lifecycle: Permanent notes are designed to last. They evolve over time as understanding deepens, but they are never "processed away" like fleeting notes. They are the enduring assets of the knowledge system.
In practice: Concept explanations, personal insights, synthesized arguments, original ideas, principles you've derived.
Extended Taxonomy
Beyond the core three, many PKM practitioners add additional types:
Hub Notes / Maps of Content (MOCs)
Index notes that organize clusters of related permanent notes. They do not contain new ideas themselves; they provide navigational structure. See Linking Your Thinking.
Evergreen Notes
Andy Matuschak's refinement of permanent notes, emphasizing continuous development and densely linked concept-oriented notes. See Evergreen Notes.
Source Summaries
Comprehensive notes about a single source (a book, a course, a major article). These go deeper than a literature note: they synthesize the source's key arguments, structure, and contribution. Useful for sources you want to reference repeatedly.
Daily Notes
Time-stamped journals that serve as the capture inbox. See Daily Notes.
The Processing Pipeline
The taxonomy implies a processing direction:
Fleeting notes → Literature notes → Permanent notes → Connected knowledge graph
This is not a rigid pipeline but a general flow. Some ideas skip stages (an insight may go directly to a permanent note). The key principle is that notes should move toward greater processing, clarity, and connection over time, not accumulate unprocessed.
Common Mistakes
- Treating everything as permanent: Flooding the system with unprocessed captures disguised as permanent notes
- Never promoting: Letting fleeting notes pile up without review
- Skipping your own words: Copy-pasting quotes without processing them into your own understanding
- Over-categorizing: Creating too many note types and spending more time classifying than thinking
Key Points
- Three core types: fleeting (temporary captures), literature (from sources), permanent (your own ideas)
- Notes flow from capture toward processed, connected knowledge
- Permanent notes are the most valuable; write them in your own words
- Extended types (MOCs, evergreen, source summaries) add structure but are not required
Open Questions
- Should AI-generated notes have their own type in the taxonomy?
- How does the taxonomy adapt when AI can process fleeting notes into permanent notes automatically?
References
- Sönke Ahrens, "How to Take Smart Notes" (2017)
- Vault: Zettelkasten is simpler than you think, Zettelkasten method, Principles of Zettelkasten