Time Traveling with Progressive Summarization

Better highlighting and note-taking techniques. A short guide to Progressive Summarization.

Why do Progressive Summarization

Progressive Summarization (PS) is an annotation technique that’s so simple it makes you wonder why no one else has thought of it before. It involves multiple passes, and you don’t have to do it all in one sitting. Here’s why you should do it.

Capturing information in the digital age is easy. So easy, in fact, that you can capture everything and forget about it. I bet you have a collection of notes somewhere gathering digital dust.

Information hoarding is a problem. 

We hoard information because it gives us an illusion of knowledge. Ever consumed so much information that you feel like you’re getting smarter?

There’s nothing wrong with this if your goal is just to enjoy it and nothing more. But if your goal is to actually get smarter, then we need to smash some misconceptions.

Knowledge jiu-jitsu

You have to wrestle with information in order to turn it into knowledge. Once we’ve wrestled with it, then we’ve learned it.

We wrestle clumsily through a mess of highlighters, margin annotations, or notebook scribbles. While it sorta works, there’s a better way.

For most of us, taking notes is an ephemeral thing. We take notes, use them, and then throw them away. But what if we can perpetually use these notes over and over again for the rest of our lives? This means less knowledge jiu-jitsu and more distilled, ready-to-use wisdom.

When making notes for life, the trick is to leverage on the “present bias”. Write for the laziest, most forgetful version of your future self. Future you has no idea and no context about what your notes are about right now. They cannot access how it feels for you at this moment, where multiple mental nodes are active and things make sense, even though your notes are just a flurry of vague phrases. 

In other words, write as if the person who will read them is reading it for the first time.

Present you isn’t entirely sure what kind of info you might need in the future either. That’s why we become information pack rats, saving every bit of info “just in case” we need it. We don’t know what we might need, so we want to leave enough context for us to understand what we saved in the past. We need enough depth of context in order for our notes to be useful.

Before your brain reads anything your eye scans it.

The problem with maximizing depth is having to read through pages and pages of words that might not be useful. This isn’t efficient. Progressive Summarization’s answer is to make notes skimmable by making key ideas pop. This widens the breadth we can cover in a single work session. The danger with this is if an idea gets too condensed. We lose the context our future self needs, and end up having to re-read the entire thing all over again.

Progressive summarization is the intersection between the two, balancing both breadth and depth of context. Having multiple layers of notes in different “purities” makes notes comprehensive. Annotations are designed for notes to be easily skimmable and easily understood in the context of the text itself, not away from it. Like a distillation set-up, Progressive Summarization works by purifying ideas further and further to its purest form.

Progressive Summarization sweet spot venn diagram Celz Alejandro
Overlap depth and breadth and you get the Progressive Summarization sweet spot.

Time traveling

Perhaps more importantly, Progressive Summarization helps you “time-travel” using your notes. By annotating and emphasizing certain key phrases and summarizing them, your future self can switch through different nodes of memories with ease, like picking ripe fruits from a vineyard that you’ve planted and tended yourself. These notes hold past states of mind, ready to be revisited at a moment’s notice.

How to do Progressive Summarization

If you want to learn more about Progressive Summarization, you should really read about it on Tiago Forte’s site. He gives an in-depth explanation for everything PS.

Here’s a tightly condensed version, to get the ball rolling. You’ll need a program that allows you to highlight, take notes, and format the text. These principles may be applied to physical notes, but only to an extent.

Note: Not all layers are applicable to every note, just those that look the most insightful or potentially useful. More on this later.

Layers of Progressive Summarization: The Rules, and How to Break Them

Layer 0: The original source material

The 0th layer is the original content to be summarized (books, articles, videos, etc.). It’s not recommended to save these, since we want to avoid mindless annotation. Take notes using your own words from this original source material for Layer 1, and be sure to link back on it in case you’ll need it, but don’t progressively summarize on layer 0 [1].

Layer 1: Initial notes, in complete sentences and written in your own words [2]

This is the initial note-taking process. By this, I mean that it should be summarized in your own words. Write in complete sentences, never in phrases. None of them should be direct quotations either [2]. Layer 1 notes include:

  • a paragraph from a book you’re reading
  • a long summary you’ve written from an article you’ve read
  • some thoughts you’ve voice-recorded while in traffic
  • some Kindle book highlights

Layer 2: Initial emphasis by bolding complete ideas.

Bold all the parts that seem interesting. There is no right or wrong here, so don’t think about it too much. Just choose what resonates with you.

How much should you bold? You want it to be short enough to be skimmable, but not too short that it doesn’t contain a single idea. Likewise, you want it to be long enough to hold a single thought, but not too long that you’re emphasizing everything.


Layer 3: Secondary emphasis by highlighting the best of the bolded text.

Highlight the best parts of all the bolded parts (and only the bolded parts), to compress the ideas even further. The highlighted phrases make your notes pop out. This makes skimming very easy and makes finding relevant notes much easier.

Layer 4: Short summary on top of existing notes.

Making your own summary further purifies your own thoughts. This forces you to think back and reflect on the material you’ve just read. Place this on top of your notes. If this were our distillation set-up, this would be the end goal. You have now obtained the purest form of your idea.

Remember, you don’t have to do this for all your notes, just those you feel useful now or in the foreseeable future.

Layer 5: Remix the ideas. 

Let’s stretch our purification analogy further. If our 4th layer is already pure, then what use would doing the 5th layer be?

If the first 4 layers are purification, then the 5th layer is alchemy.

By combining two ideas together, we make them clash to make something new.

This knowledge alchemy is only for a select few of the best ideas that you want to become part of you. Remixing means analyzing layers 1-4 in different ways and making something else from it entirely, putting your own unique spin on it. It’s developing new combinations of ideas and creating a new flavor from it, one the world may or may not have seen before, but one that is entirely yours.

Progressive Summarization in action: big and small

The best way to understand Progressive Summarization is to see it in action. 

Big post example: Book summary and synthesis

Layer 0: Antifragile book as a source material

Layer 1: Taking notes while reading

Layers 2 and 3: Additional emphasis

Layer 4: Executive Summary Turned Value Post

Clicking on the link will take you to the original post.

Layer 5: Book Summary in Blog

Progressive Summarization in the web. The example is a book summary of Antifragile written by Celz Alejandro

Here you can see that I’ve retained the bold passages along with the highlights. You can look at the entire post here. Most of my posts are progressively summarized until the 3rd layer (highlights).

That summary was remixed with other ideas I picked up from various sources, and injected my own flavor into it as well, based on the unique lens through which I view the world.

Small remix example: social media posting

There was a webinar done by David Perell and Matthew Kobach a few weeks ago on How to Crush it on Twitter (@celzalejandro). While I shared it on social media as part of my 4th-5th layer remix, you can go even smaller. Here’s me sharing my takeaways with a friend:

Progressive Summarization small remix in social media posting

This became the first “draft” of the value post I put up on LinkedIn, and the ideas distilled here are my go to principles for writing and tweeting on social media.

Progressive Summarization Tips

1. PS is like a stack of pancakes. Often you need just 1 layer.

Progressive Summarization is like a stack of pancakes. Often you'd want to have 5 layers, but that'll make you sick.
Eating five-layer pancakes all the time might seem fun, but I’m sure you’d get pretty sick of it.

Notes don’t need all layers to be effective. Some things only need to be bold and highlighted, and some things need to be remixed immediately.

Progressive Summarization is like having a stack of pancakes.

Most times, a single pancake is enough. Maybe two. Other times, you really, reeally want a stack of 5 pancakes. Those times are (should be!) very rare, just like in doing the 5th layer of PS. Do too much and it’ll make you lethargic slow down your thinking, instead of energizing you for your next tasks.

2. Break the “Rules”

[1] I’d argue that you can apply other layers of Progressive Summarization directly to layer 0, but only when you need to analyze direct passages from the material.

[2] I break this rule a lot.

As a writer, I tend to save interesting phrases that I can incorporate in my work. I also save customer testimonials in their original phrasing. This retains the original emotion and relatability that would otherwise be lost. People don’t communicate in well-polished sentences. Often there’s a mixture of slang, punctuations, and other quirky things that makes writing feel more conversational. I preserve samples of these as-is.

3. Stretching some PS layers for specialized use

PS was developed for knowledge work, but anyone can benefit from it.

One-color highlights are enough for most purposes. For information-dense material that requires lots of brain power to consume, multi-color highlights can make PS even more powerful.

How can you condense something when every single sentence is important? What if the idea that you only need to highlight a very small number of phrases just doesn’t cut it?

Answer: multi-color highlighting. Oh, and med school.

There’s no other population that understands the importance of progressive summarization than medical students. Especially when it comes to remixing knowledge and absorbing it quickly.

Medical transes or medical transcriptions are basically dense class notes. Think of it like an entire document made up of layer 4 notes. Transes are made up of phrases, bullet points, and diagrams.

While the concept of transes are widely-known, they’re not exactly open-source. Hence the example below. While not an actual trans, the technique applied is similar to PS with some additional annotation. Such mark-making is similar to the 5th PS layer.

You’re remixing the ideas in your head and turning it into knowledge in order to learn it quickly. Connecting different pieces of knowledge together in different ways helps retain information further.

Progressive Summarization for med school notes, med transes, and information dense material Celz Alejandro

A 4-color highlighting system can be separated per color. The additional layer of distinction is a visual to treat each group separately. On the other hand, items with the same color indicate similarities and tells your brain to look for the common thread.

Multi-color highlighting breaks through the density of heavy material. Students can take advantage of this technique but can be used by anyone for anything that needs more time to digest and analyze.

4. There is no perfect.

Progressive Summarization is supposed to make you more productive.

If it adds stress to your work flow, stop. Breathe.

The real purpose of Progressive Summarization is to give you more time to do what you need to do, so don’t spend excessive amounts of time trying to get your highlights right. There is no “right way”. Just do whatever motivates you to take the next step.

You don’t have to do all the highlights each time you read something. Instead, do it opportunistically, or just when you need to. This is to prevent procrastination from doing actual work.

Remember: We’re not in the business of doing busy work to make ourselves feel productive, we’re here to actually be productive.

Life with Progressive Summarization

I’ve been doing PS for a few months now and I can say that this has been the best system for me. It gives the right balance between having context about the topic without being too overwhelming and having enough emphasis so I can zoom through and skim when needed.


Progressive Summarization is a simple way to help you retain more information and to help you surface relevant information as fast as possible. Although it seems like such a simple highlighting technique, it really helps you more things done and I’ve found myself using it over and over again.


Credits: A big thank you to fellow BASB Envoy Raphael Sisa for the feedback (psst, subscribe to his newsletter!), Paolo Castillo, Meoni Bergara, Liana Jovellanos, and Joan Ravalo for letting me ask lots and lots of questions about their notes, and again to Meoni for giving me a walkthrough of her note-taking habits.

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