Introduction: PARA’s personal information organization method was previously recommended in the product meditation book, and one of the reference sources of its method was found "Zettelkasten  ", a sociologist and system theorist from Germany-Nicholas Niklas Luhmann
When studying Luhmann's Zettelkasten method, what inspired me the most was not to learn this method, but to get rid of some inherent concepts, such as:
• I thought that writing is output, but writing is not the result of thinking, but the medium in which thinking occurs. • One of the most cheating myths about creativity is that it happens from scratch. I often start to create with a blank sheet of paper (a bad habit I developed in previous paintings), but ignores that no one can create from scratch. • When encountering difficulties, we always stumbling, but in fact, it is not bad to proceed along the most interesting road, and it is okay to carry out multiple projects at the same time. • I like full text collection, but in fact collection is more like carrying information (rather than processing), and there is no Increase any knowledge. •I always want to establish a perfect classification, but in fact the classification is like a building. Once it is designed and improved, it will face the problem of complete reconstruction. And our absorbing knowledge is more like a process in which neural circuits are continuously strengthened/weakened, and structures will slowly grow out after collection.
Luhmann used this method to accumulate 90,000 knowledge cards and wrote 60 books and numerous other publications in his lifetime. In 1968, when Luhmann published his thesis at the new university, he received a questionnaire about the content of his research. His answer was this: " Project: Sociological Theory. Duration: 30 years. Cost: Zero .」
This method of recording and organizing knowledge is widely known through the book "How to take smart notes  " by German writer Sönke Ahrens . This book introduces the causes and consequences of the card box note-taking method and a detailed guide. A lot of content in this article is quoted from this book and related introductions. Another:
• This article does not provide a detailed method of using Zettelkasten. If you are interested, you can click "Read the full text" to find a reference link at the end, which has a very specific implementation method. • This article is regarded as an application of Zettelkasten's thoughts. It is not really "original" (that is, it is not typed out one by one), but a lot of content is a "collage" of knowledge and a large number of deletions and own opinions. Some prejudices and misunderstandings should be considered carefully when reading.
What is Zettelkasten
Zettelkasten is German and English is Slip-box, which translates to note box, note box, card box, card box; referred to as card box note-taking method, or card-box note-taking method. 
In essence, it is not a "skill" but a "process", a method of storing and organizing knowledge, expanding memory, and generating new connections and ideas . To put it simply, it is to collect the knowledge you are interested in or think you will use in the future, and then use a standardized way to process these notes, to establish the connection between the notes for your use.
As a tool, Zettelkasten is a box (or a box cabinet) for holding index cards or paper strips (Zettel). Each card has a piece of information, an index and a source of information. The index can be an ongoing number, date and time, or anything you can use as a unique identifier. In most cases, this information is short and should be limited to a few words or sentences. The size of the card helps keep it simple. Pictures and other forms of information can also be used.
But be careful not to just copy the information. You must write in your own words , in a way you understand. Every time you consume new information from elsewhere, you must process that information in a way that you understand. Don't worry about not being thoroughly understood, because you need to mark the source of the information on the card and more Metadata to facilitate the search for the source information in the future. In fact, the key idea here is to make permanent notes for your future . Write it as if it were written to others, writing in a clear and concise way. You can also think of it as a piece of content on Wikipedia. It may not be outstanding, but the record is well-documented and indexed.
After writing the card, put it in the box. Each box contains a set of interrelated cards. In the box, the cards can be further organized by placing tags with keywords, so that you can more easily find the cards in the big box. Don't worry about the structure . A key idea of this method is to let the category or topic "organically" appear in front of you when adding notes. Pre-designing the structure, categories, and levels will create an information highway. The advantage is that you can quickly reach the place you want to go, but the disadvantage is that you never know where other paths can lead.
Over time, you will add more and more cards. To unleash its full potential, you must manually link cards by using box tags, keywords, and the index of the cards you quote. The connection form of the card can also be many kinds, either without connection, or with many cards. To connect them, you have to do a lot of searching and searching in the structure of Zettelkasten, but this is also part of its design-randomly discovering some previously ignored connection methods and missing knowledge.
The process of connecting the cards is like your brain.  By connecting missing information points, you create interconnected knowledge clusters that emphasize the importance of information based on the number of connections. It can also help you remember where to find a message. Connected information will accelerate your breadth of thinking and overall value. The card size is limited, in fact, it is to encourage the use of it to connect knowledge rather than record knowledge . Once you write down a message or idea and connect it with the relevant card, you can throw it out of your mind-the disadvantage of the traditional inbox idea is that it only archives but no connection. In the end The inbox becomes a trash can, and all ideas are thrown away together.
Application of Zettelkasten 
Luhmann once said that if you use a certain structure (such as a table of contents in a book), you will follow a fixed structure, which will affect your thinking and limit your path through the knowledge base. This is why the indexing system you choose is very important to the scalability of your Zettelkasten. When assigning a new index, flexibility is essential , such as inserting a new card between two existing cards while retaining a meaningful index. The index system is the backbone of your Zittle Caston.
So, what is a good indexing system? Luhmann uses a level index, which allows him to add new cards to his structure while maintaining their order. We start with a very basic Zettel structure, which contains only three cards.
As you can see, there is a continuous number on these cards. If we want to know more about the details of the second card. We can continue this line by adding card number 2a, and then using card number 2b, 2c, etc.
If we now want to have more details on one of the deeper cards, we only need to start with a new sequence starting at 1. This can be done forever if you want. Finally, we have a structure that provides a quick, relatively small overview of the knowledge base, but if you go down a path, you will dive into the details. This structure can also be flattened to form an information flow, for example, it can be written as a book like this.
The thinking behind Zettelkasten
Change of ideas 
1. Writing is not the result of thinking, but the medium in which thinking occurs.
Even if you are not planning to write a book, you still need a way to organize your thoughts and track the information you consume. If you want to learn and remember something for a long time, you must write it down. If you want to understand an idea, you must translate it into your own language and put it in your own knowledge system. Writing is not only to express fully formed opinions, but also to form opinions worth sharing in the first time .
Writing can improve a person's thinking ability very well, because it forces you to consume information from a deeper level. Just reading more does not mean you have more or better ideas. Just like learning to swim, you must learn through practice, not just learning on paper . Therefore, the challenge of writing and learning is not in learning, but in understanding. When you really understand something, it is placed in a framework of related ideas and meanings, which makes it easier to remember. (You can refer to the book "World View")
When you consume information, having a clear, tangible goal will completely change the way you process information. You will be more focused and more curious. You will not waste time writing down every detail, trying to make a perfect record of everything you say. Instead, you will learn the basics as effectively as possible so that you can get to the point where open questions arise, because these are the only questions worth writing about.
Deliberate practice is the best way to improve anything. In this case, you are deliberately practicing the most basic skill: thinking. Even if you have never really published a line of articles, when you do anything, as if nothing matters except writing, you will greatly improve all aspects of your thinking.
2. No one will start a thing from scratch (and don’t do it)
One of the most cheating myths about creativity is that it happened from scratch. Blank pages, white canvases, and empty stages-our most romantic and universal art theme seems to imply that "starting from scratch" is the essence of creativity.
This belief is reinforced by typical writing teaching methods: we are told to "choose a topic" as the necessary first step, then conduct research, discussion and analysis, and finally draw conclusions. But before you read an interesting topic, how do you decide it is it? Before you know how to ask a good question, you must immerse yourself in research. The decision to read one topic versus another does not appear in a vacuum. It usually comes from existing interest or understanding.
This is the core of the creative process: before you choose what you want to write, you must work hard to research and accumulate . Ideally, you should start research before you start creating, so that once you decide on a topic, you have weeks, months, or even years of rich material available. This is why it is so important that you put information in the "second brain".
As we read, we build a growing externalized pool of thoughts. When it comes time to create, we are not following blindly fabricated plans taken from our unreliable brains . We look through notes, follow interest, curiosity, and intuition, which all come from the actual work of reading, thinking, discussing, and taking notes. We no longer have to face the blank screen and impossibly request "want to write something".
No one really creates from scratch . Anything they come up with must come from previous experience, research or other insights. But because they did not act on this fact, they cannot trace the source. They have neither supporting materials nor accurate sources. Since they did not take notes from the beginning, they either start with something completely new (which is risky) or go back to their own history (which is boring).
Taking notes (and placing them in your second brain) can free you from the traditional linear writing path. It allows you to systematically extract information from linear resources, mix them together, reorganize them until new patterns appear, and then convert them into linear text for others to read.
When you find that there is not enough things to write before and there are too many things to write, you will find the changes brought about by these habits.
3. Always follow the most interesting path, and there is nothing wrong with doing multiple projects at the same time
In most cases, students fail not because of lack of ability, but because they lose personal contact with what they are learning. "Even very smart students fail in their studies. The most common reason is that they cannot see the meaning of what they should learn (Balduf, 2009) and cannot connect it to their personal goals (Glynn, 2009). Or lack the ability to autonomously control their own learning (Reeve 2006; Reeve, 2009)"
This is why we must spend as much time as possible on things that interest us. This is not an indulgence, but an important reason that makes our work sustainable and successful. This suggestion runs counter to the typical planning method we have learned. We are told to "make a detailed plan." Success depends on our persistence with this plan. So if for some reason we have some new ideas, in most cases we will be suppressed-because we will be suppressed. The accusation said: You are distracted.
But the history of science is full of accidental discoveries, such as penicillin, such as DNA. DNA research started with a grant, and its research goal is to find a cure for cancer. But in the process of their work, the research team followed their intuition and interest and developed practical research projects along the way (Rheinberg 1997). If they stick to their original plan, they may not discover a cure for cancer, and certainly not the structure of DNA.
The plan is to give us a sense of control, but more importantly, to truly control the situation, which means to be able to direct our work in directions that we think are interesting and relevant. According to a 2006 study by psychology professor Arlen Moller, “When people have a sense of autonomy in choosing (work content), their energy for subsequent tasks does not decrease” (Moller 2006). In other words, when we choose a job we are interested in, we don't need much willpower .
Our sense of accomplishment depends on continuous progress. But in creative work, problems will change and new directions will emerge. This is the essence of insight. Therefore, we do not want to work in accordance with a rigid workflow, which will be threatened by unexpected events. We need to be able to make small, continuous adjustments to keep our interests, motivation, and work aligned. By breaking down the writing work into independent steps, getting quick feedback on each step, and always following the path of the most insightful, unexpected insights can become the driving force of our work.
Luhmann never forces himself to do anything, only those things that are easy for him to do: " When I get stuck for a while, I leave it to do other things. " Just like in a game Similarly, if you encounter resistance or the strength of your opponent, you should not resist it, but put him aside first.
In addition, the full potential of the external thinking system can only be realized when you are working on multiple projects of interest at the same time. Because you don't know what you will encounter during the research process, you will read many books, but these books may not have the answers you want. But the only way to find the insights contained in a book is to read it, so you might as well read and take notes productively. Take a little extra time to record the best ideas you come across—regardless of whether you know how they will be used in the end—after you archive them, at least in the future you will most likely find him again "by chance". Focusing too much on finding answers will waste a lot of time spent in the process.
About information acquisition and organization
1. Standardized behavior can stimulate creativity
Before container transportation, the efficiency of global transportation was very low, and all supporting facilities were non-standardized. The arrival of global trade is because the entire transportation process is designed around containers, which makes the output and input efficiency extremely high, which in turn promotes the take-off of trade in many regions.
The same is true in daily records. To this day, many people still take notes in a temporary, random way—even many people don’t take notes. If they see an interesting golden sentence, they will underline it. If they want to comment, they will write it in the blank space. If they have a good idea, they will write it in any notebook (or phone memo) they have. If an article seems important enough, they may try to save an excerpt. This allows them to record content in many different formats in many different places with different recording methods. This also means that when they start writing, they must first conduct a large-scale collection and sorting of these messy records - or directly retrieve them from their heads.
Zettelkasten is like a container of thought, which stores a lot of knowledge you have accumulated in the past. Instead of "inventing" a new way of taking notes for every type of information you read, it is better to use a fully standardized format every time. No matter what these notes contain, which topic they are related to, or the medium through which they are spread-you treat each note exactly the same way.
It is the standardization of this kind of notes that allows your information to be established in one place, from quantitative change to qualitative change. Without a standard format, although the amount of collected data will increase, the time for sorting will also increase, or it will eventually become a trash can. The universal format eliminates unnecessary complexity and confusion. Just like Lego bricks, standardized notes can be easily assembled together and assembled into endless shapes without losing the information they contain.
The same principle applies to the steps we use to process notes. Just like when there is no container to transport something to every place, the "interface" must be redesigned. If the standard is followed, everything will become very simple. For example, writing notes is not difficult. It is not difficult to turn a group of notes into an outline. Turning a work outline full of relevant arguments into a rough draft is not a challenge. It is also trivial to polish a well-conceived rough draft into a final draft.
By standardizing and simplifying the format and processing steps of notes, we can focus more on the following processes: thinking, reflecting, writing, discussing, testing and sharing. This is a value-added work, and now we have time to complete it more efficiently.
2. Collection is useless, you need to organize the information yourself
Most of the time we fall into the "collector's fallacy", feeling that collecting is learning, but in fact "knowing something" is not "knowing something". Collection is more like carrying information (rather than processing) without adding any knowledge on the way.
The correct approach should be: Research, Read, Assimilate; rinse and repeat. There is no need to capture 100% of the information. The brain is like a filter. Only by constantly changing the filter can information be truly input to the brain (the subconscious will filter out a lot of useless information by default, which is difficult to detect)
Information is collected by your senses. Information is not an attribute of everything in this world, but a part of our interpretation of them. Therefore, when consuming information, continuous recording is a process of interpretation and a process of "writing" into the brain.
Reading is a constructivist activity: information must be created from existing data. This means that you need a creator to add your own insights. Your job is to construct the meaning of the text, create information, and record it, because your own interpretation is the most important.
3. Barbell reading method (repeated exercise of key parts)
Although we want to improve the efficiency of information absorption, most of the so-called "fast reading" techniques are either to increase reading speed and reduce comprehension, or to skip most of the content. Another problem with trying to increase reading speed is that they emphasize the absolute amount of text you consume. The most important and easily overlooked part of the reading process is the processing of the content.
The problem that often arises is: either read carefully and waste a lot of time on bad books. Either increase the reading speed, but in fact, the whole book does not fully understand a book-because the information is not transformed into knowledge and skills-the information is just an opportunity. There is no meaning without using information.
The steps and principles of the barbell reading method
• Read the book quickly, don’t skip it, but mark out the useful information that you are interested in. • Read it again, and read only the parts you marked. And take good notes and build a structure
View Image real reading is not a passive process, in this process you just create an influx of information. It includes in-depth processing, thinking, and writing, which are all things you have read and are connected with things you already know. Only when the three parts of reading, thinking and writing are combined can you bring real changes to your brain and make you a better thinker.
4. Why classification is a bad idea
Creating categories is a top-down process. You start with the structure and then file the materials. The comment must conform to this structure. Our brains do not work according to classification, at least not at first. It may invent categories to improve efficiency, but we will not start our lives with categories that already exist-our lives are chaotic at the beginning.
When knowledge grows, the network of things we know will grow organically (instead of building a certain structure, more like plants. Not buildings)
The classification is like a building, once it is designed and improved, it faces the problem of complete reconstruction. And our absorbing knowledge is more like a process in which neural circuits are continuously strengthened/weakened, and structures will slowly grow out after collection.
Information is subjectively understood by individuals, labeled to establish connections and become knowledge. Everyone's system is different, so it must be personalized and growing. The traditional classification cannot satisfy this growing state.
Luhmann often said that he never forced himself to do things he didn't like to do. "I only do things that are easy to do. I only write when I know how to do it right away. If I waver a little bit, I will put things aside and do other things." (Luhmann , 1987).
The figure below is a chart of information visualization made from the accumulation of Luhmann's life. I hope that from today, you can start accumulating your own knowledge base.