What is a second brain and how does it work

By Gianluca Bonomo — Technology Trainer and Instructor

Published on October 12, 2026

Have you ever known you wrote something down, and still couldn't find it? Last year's quote, an idea scribbled on a scrap of paper, the link to a great article: it all ended up who knows where.

A second brain is built for exactly this: one place, in order, where the things you want to remember are waiting for you. And today, with artificial intelligence, that place doesn't just store things: it answers, connects and prepares.

1. The problem: I have everything, but I can't find anything

Your brain is brilliant at thinking and terrible at filing.

Think of Marta, who runs a plant shop in Bergamo, in northern Italy. Her suppliers are in her phone contacts, her prices in an Excel sheet, her window display ideas in phone notes, customer photos in WhatsApp and quotes in a folder called “New folder (3)”. When she needs something, she searches five places, and sometimes gives up.

That isn't being disorganised, it's normal. Our head is built to think, not to store. Ask it to do both and it does one well. The rest has to go outside, to a reliable place.

2. What a second brain is

A second brain is a personal digital archive made of notes, documents, ideas, links and reminders, organised so you can find and reuse what's inside.

The easiest comparison is a restaurant kitchen. The cook doesn't remember where each ingredient is: there is a pantry with labelled shelves. That way, while cooking, they think about the dish, not about the coarse salt. The second brain is your head's pantry.

2.1 What it is not

• It is not one specific app. You can build it with Word, a folder on your computer, Obsidian or Google Drive.
• It is not a diary. A diary is written and reread now and then. A second brain is consulted and used.
• It is not an endless collection. Saving everything is pointless: save what will be useful.

3. Where the idea comes from

The idea is older than computers. In 1945 the American scientist Vannevar Bush imagined the Memex, a mechanical desk where each person would keep books, letters and notes, linking them together. It was a dream, but it already looked a lot like what we use today.

Then there is the German sociologist Niklas Luhmann, who for decades wrote down his ideas on paper cards, linking them with numbers. His card index (the Zettelkasten, “box of slips”) held tens of thousands of them and is considered the ancestor of many of today's methods.

The name “second brain” was popularised by Tiago Forte, an American trainer, with his 2022 book Building a Second Brain. Forte didn't invent the personal archive: he turned it into a simple method anyone can follow. Let's see it.

4. How it works: the CODE method

Forte's method is remembered through four letters, CODE. They are four actions, always done in the same order, like the steps of a recipe.

5. Where things go: the PARA method

To know where each thing goes, Forte proposes PARA: four folders that are enough for almost a whole life. The trick is to sort by usefulness, not by topic: what counts is what you need it for now, not what it is about.

See how handy it is? Things move from one folder to another as life changes. Nothing is thrown away, but what you don't need leaves your desk.

6. What goes inside a second brain

Inside goes whatever you need to work and live. Nothing exotic: ordinary files are enough.

• Notes: ideas, summaries of books or courses, meeting minutes.
• Documents: quotes, contracts, data sheets, PDFs.
• Profiles: one page per client, supplier, project or topic.
• Procedures: “how I do it when...”, written once and reused forever.
• Inspiration: links, images, quotes that struck you.

7. Artificial intelligence enters the scene

Until a few years ago a second brain was a passive archive: you put things in, you searched, you connected. Today you can pair it with an artificial intelligence (AI) that reads your notes and answers using them.

Imagine a lightning-fast librarian who has read your whole folder. You ask: “What did I decide with supplier B?” They don't make things up: they go to the shelf, take the right pages, read them out and tell you which page the answer comes from.

7.1 How it reads your files

Chatbots don't hold your whole folder in their head: it would be far too big. They work in two ways. The first is simple: attach the files to the conversation, and the AI reads them on the spot. The second is called RAG (Retrieval Augmented Generation): first the AI searches your files for the pieces related to your question, then it reads them and answers.

In practice: search finds the pages, reading turns them into an answer. That's why the clearer and better titled your files are, the better the answer.

7.2 What changes in practice

8. What it is for, day by day

Here are four real uses you can start with tomorrow.

1. Answering a client. Ask: “What did we promise them in June?” and the AI finds it in your minutes.
2. Preparing a lesson or an article. Put scattered notes together and ask for an outline based on them.
3. Summarising a meeting. Paste your notes and get decisions and tasks for each person.
4. Finding an idea. “What was that thing about packaging I wrote in spring?”

9. The limits: what can go wrong

A second brain with AI is powerful, but it is not a magic wand. There are four things to know, and it's better to know them first.

I want to be very clear on one point: there is no perfect tool. There is the tool you actually use. It will change over the years, and that's fine: if your files are simple, you take them with you.

10. How to start in twenty minutes

You don't need to buy anything to begin. You need a folder and twenty minutes of goodwill.

1. Create a folder called Second Brain on your computer.
2. Inside it, create the four PARA folders: Projects, Areas, Resources, Archive.
3. Choose one real project you have right now and put its files in.
4. Write a half-page file: who you are, what you do, what you're working on now.
5. Then move on to the second article: there I explain how to connect AI and which tools are free and which are not.

Practical exercise

Twenty minutes, pen and paper or a text file. No software needed.

1. List the places where you keep your information today (phone, email, notebooks, folders, photos).
2. Pick a project you're working on and write in one line the result you want and by when.
3. Answer the PARA questions: does that project go in Projects or Areas? Why?
4. Find five things you need for that project and write where they are right now.
5. Imagine asking an assistant: “What do I already know about this project?” What would it answer reading only what you have written?

Questions that come up in class

Glossary

Further reading

• Tiago Forte, Building a Second Brain, 2022 — the CODE and PARA methods
• Vannevar Bush, As We May Think, The Atlantic, 1945 — the Memex idea
• Official documentation of Claude, ChatGPT, Gemini and NotebookLM — projects, files and connectors, consulted in October 2026
• Gianluca Bonomo, Niente paura, è solo IA — reference book (Italian)