What Do We Mean When We Say "Bottom-Up?"
The term "bottom-up" is commonly used to characterize "flat" note-taking systems that reject both hierarchy and topical folders, ones that draw inspiration from Niklas Luhmann's zettelkasten practice and writings. However, the term still retains a degree of ambiguity, functioning as shorthand for working with ideas "organically" or in a way that "more closely resembles how our brain works." Despite its frequent use, the question remains: what do we mean when we describe the zettelkasten as a network of ideas structured bottom-up?
How the Term "Bottom-Up" Is Understood Outside PKM
To better understand the term "bottom-up" it can be helpful to look at how it's used outside the PKM community.
In politics, "bottom-up" refers to "direct democracy," wherein people have an immediate role in the political process, bypassing representative intermediaries.1 Similarly, in management discourse, the term "bottom-up" can signify "democratic management" policies where employees are "actively invited to participate in goal setting and decision-making."2 In psychology, bottom-up refers to perception which is "driven" by external stimuli, where incoming sensory data "is interpreted based on its inherent properties without reliance on pre-existing knowledge or concepts."3 In the field of design, bottom-up refers to identified problems and environmental conditions that determine the look, feel, and fabrication of the final product.4 In each case, working "bottom-up" pertains to the manner in which a sense of wholeness and coherence emerges from the information collected from the individual components that constitute or contribute to the whole.
Top-down approaches work in the opposite direction. Instead of allowing the materials to inform the whole, a perception of what the whole should be determines which materials are allowed to be used. It's "having an overarching concept before working out the details."5 To put it another way:
"Top-down thinking is when you plan a meal, find recipes, get ingredients, and then cook the meal. You started with the result and worked your way down to what was needed to make it happen. Bottom-up is when you rifle through your cabinets and fridge to try to cobble together something edible. You start with the components and figure out what you can do."6
A Luhmann-Style Zettelkasten Is Formed Out of Its Ingredients
A Luhmann-style zettelkasten is a bottom-up approach to managing information and knowledge. Structured "heterarchically,"7 the zettelkasten lacks both predefined categories and topical folders. It is, by design, a distributed network of ideas, one without thematic centers to which ideas must relate. To better understand this, let's first look at how we've been typically taught to import and organize information.
Importing New Ideas
Let's say you've captured a thought about tarot. In a system organized top-down with predefined categories, your initial steps to integrate this note would involve accessing a top-level "Religion" category, then accessing an "Occult" subcategory, followed by a "Practices" subcategory, where you would eventually find and land on a subcategory labeled "Tarot." You would then import the note into this section of your archive, and, if you were partial to linking your captured thoughts, find other notes "about tarot" to which it could be connected. This note would live among others of the same topic, only to be called upon when the topic was explored. A bottom-up approach, such as the one presented by Niklas Luhmann, could not be more different.
In a bottom-up system, topics are regularly interrogated. Is your note really "about tarot," or does it touch on a variety of related and unrelated themes? What if your "tarot note" expressed a positive sentiment about your having completed a year-long course on tarot? In this case, the note could connect to others regarding accomplishment, perseverance, or commitment. Since the note spoke to online education, it might also connect to others dealing with online courses, pandemic challenges, or working remotely. While the note may still link to others discussing tarot and tarot practices, these relationships would not be strictly dictated. In a bottom-up system, ideas are free to interact across topic, leading to "unexpected linkings," "heterogeneous things," and "combinatorial possibilities which were never planned, never preconceived."8
Finding Ideas to Work With
Locating ideas within a Luhmann-style zettelkasten also takes the form of a bottom-up approach, albeit often aided by top-down views of the slip-box's contents. Alphanumeric IDs, keyword indexes, hub notes, and structure notes (all used, though not necessarily named by Niklas Luhmann) help the note maker navigate their network of ideas.
Alphanumeric IDs allow note makers to trace trains of thought throughout the anarchic, distributed network of ideas. Hub notes point toward areas of developing themes. Structure notes provide "places" to unpack and explore these areas of interest.9 Niklas Luhmann's keyword index, though a high-level view of the distribution of notes, was far more suggestive than it was comprehensive. Having at most four references to notes containing the same keyword (in an archive of sixty thousand notes / ZK II), the austerity of the keyword index's entries speaks to Luhmann's appreciation of meandering through relationships rather than searching for exact "hits."10 In short, the keyword index appears to have been somewhat of a top-down nod to the feral nature of the slip-box's bottom-up structure.
Writing With a Zettelkasten Is Both Top-Down and Bottom-Up
Despite its structure emerging bottom-up, writing with a zettelkasten—like all writing—involves both bottom-up and top-down approaches.
Adopting a bottom-up approach to writing allows ideas and connections to guide the process. A writer starts with what they have—ideas captured in notes—and lets them determine the direction of the project. Sönke Ahrens, drawing inspiration from Niklas Luhmann's concept of "lumps forming," refers to "clusters" within the slip-box, which reveal areas of increased activity that provide insights into potentially fruitful writing topics.11 Well-developed trains of thought, distinguished by extensive alphanumeric IDs or detailed structure notes, act as reliable indicators.
By contrast, in a top-down approach to writing, the writer begins with a predetermined topic that is then supported by relevant ideas pulled from the zettelkasten. While a bottom-up approach embraces the emergent nature of ideas, top-down methods provide a targeted framework, allowing the writer to curate and gather materials with a predetermined goal in mind.
In practice, however, a writer does not choose one approach over the other. Instead, the writing process unfolds as a dynamic interplay between top-down and bottom-up approaches. Writers will frequently oscillate between the two, adapting their strategy based on the evolving needs of their project. For example, writers may initially embrace a top-down plan, outlining a specific topic and structure, only to find that, in the act of engaging with ideas and notes stored in the slip-box, a more bottom-up, exploratory approach takes hold. Conversely, a writer might start bottom-up, allowing the network of ideas to reveal a topic, and then shift into a top-down approach once the thematic focus is defined. This oscillation reflects the flexibility inherent in the writing process, where the natural ebb and flow between these approaches contribute to a richer and more nuanced final result.
Start at the Bottom. Work In the Mix.
Working with a Luhmann-style zettelkasten involves a mixed bag of approaches, both bottom-up and top-down. The structure of the archive is emergent, building up from the ideas that have been incorporated. It is an anarchic distribution allowing ideas to retain their polysemantic qualities, making them highly connective. But, working with the zettelkasten is more inclusive of a diversity of approaches.
Writing—the interplay between ideas and the words we use to express them—involves both bottom-up and top-down approaches. The availability of ideas reveals topics to be discussed that must themselves be supported by new ideas. The act of writing not only transforms our thinking, but reveals the dynamic nature of the writing process itself, where initial plans yield to the evolving influence of encountered ideas, creating a continual cycle of adaptation and refinement.
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https://en.wikipedia.org/wiki/Direct_democracy. See 2008 Democratic candidate, Mike Gravel: https://en.wikipedia.org/wiki/Mike_Gravel. "Bottom-up" in politics may also refer to anarchic approaches to social organization.↩
Brewer, T. "What’s a Bottom-Up Organization." https://www.functionly.com/orginometry/org-structures/whats-a-bottom-up-organization↩
Cherry, K. (2023). "How Bottom-Up Processing Works." https://www.verywellmind.com/bottom-up-processing-and-perception-4584296↩
One of the more notable adopters of this approach to design and architecture was the Bauhaus in the early 20th century. See: Owen, C. (2009). "Bottom-up, Top-down." https://id.iit.edu/wp-content/uploads/2015/03/Bottom-up-top-down-updown09.pdf↩
Schmidt, J. https://niklas-luhmann-archiv.de/bestand/zettelkasten/tutorial↩
Luhmann, N. (1981). "Communicating with Slip Boxes: An Empirical Account." (M. Kuehn, Trans.). https://luhmann.surge.sh/communicating-with-slip-boxes↩
Fast, S. (2023). "Upgrade Atomic Thinking to Holistic Thinking." https://zettelkasten.de/posts/upgrade-atomic-to-holistic-thinking/. In his research, Johannes Schmidt found nestled among Luhmann's main notes others that appeared to produce a "larger structural outline." See: Schmidt, J. (2016). Niklas Luhmann’s Card Index: Thinking Tool, Communication Partner, Publication Machine. https://pdfs.semanticscholar.org/88f8/fa9dfbc0c2b296758dd932b871917c5c775a.pdf. Albeit, rudimentary, I believe these note to be the precursor of what we now call "structure notes."↩
Luhmann, N. ZK 2: 9/8b↩
Ahrens, S. (2017). How to Take Smart Notes. CreateSpace Independent Publishing Platform.↩