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This is the last page of the handbook. Start at page one.

What's the story behind this handbook?Expand

A year ago, I was fundraising for a startup. In the process, I met a lot of investors. It struck me how uniformly insightful they were. I had not seen anything like it before.

Their wisdom extended beyond domain expertise. They seemed to have a high-level ability to connect dots between disparate concepts with a degree of pragmatism that made me wonder, "Are these people exceptionally bright?" 

I didn't have an answer. All I knew was that they didn't seem to be innately smarter.

A couple months later, an investor friend asked me, "Have you heard of mental models?" I hadn't. I looked them up, and everything suddenly clicked: Investors didn't necessarily have greater intelligence ‚ÄĒ they aren't necessarily capable of being rocket scientists ‚ÄĒ rather they learned¬†tools¬†for making good decisions.

I didn't even known there was a toolbox to begin with.

I began researching critical thinking. I was dismayed to only find material from university lectures. Expectedly, it was dry and uninspired. Unexpectedly, it was also sparse and disjointed: There wasn't a unified framework to deploy the key 20% of critical thinking concepts into daily conversation and writing. 

And none of the examples were illuminatory. Or engaging to read.

So I decided to put the work into writing what I believe is the first holistic, layperson's guide to critical thinking.

Hopefully the way I'm presenting fallacies, biases, and models makes their relationships seem self-evident, but these topics aren't historically taught within a singular framework. Nor are they accompanied by prescriptions for refutation.

I had to rigorously think through how everything in this guide connected. And I had to generate original refutations, techniques, and models.

By the way, if you've read this far, you'd be silly to not¬†say hello on Twitter ūüėú I'll be posting there when my next handbook is out.

Don't just walk away

You're almost done! But we need to make sure this was worth your time.

Consider how we read dozens of books and articles every year. And how we participate in thousands of conversations.

Yet, how much of it do we remember? How often do we learn something that makes us think "Wow, that completely changed my perspective!" then revert to our old habits the very next day? 

Reflect on all the TED talks you've watched. Your fading memories of those are a graveyard of unapplied insights.

Similarly, the 20 minutes you spent reading this handbook was a waste of your time if you don't spend another 20 memorizing the cheat sheet at the bottom of this page.


In this guide, we've demystified arguing, deciding, and persuading.

We know that "conversational intelligence" is simply a learnable skill. To be a successful writer, speaker, or businessperson, critical thinking plays a huge part ‚ÄĒ because forming persuasive arguments is at the heart of every form of communication.

You don't need to be a math genius with a high IQ to be world-class at these skills.

So it's worth repeating: Many of the people you admire aren't necessarily unattainably smarter than you. They're likely just highly consistent in their pursuit of good conclusions. They don't let their "gut instincts" blind them.

To be like them, you'll need to start by remembering the material in this guide. The cheat sheet alone won't be enough. You'll also need to put this into practice. 

So this brings us to our final topic: debate your friends.

"I have no special talent. Curiosity, obsession, and dogged endurance combined with self-criticism have brought me to my ideas."
‚Äď Einstein

Debate your friends

Using the upcoming cheat sheet as a reference, debate your friends over the phone or in-person. 

Find out who's interested in debating you by posting something like this to Facebook:

Who wants to debate me so we can get good discussions going? Possible topics: death penalty, pardoning Edward Snowden, designer babies, the ethics of eating meat, the ethics of keeping animals in zoos, legalizing drugs, or any other topic you care about. Just leave a comment saying whether you're for or against the topic you want to debate me on, and if I'm the opposite, we'll chat!

If you make a habit of having these conversations, you'll gradually become wise on all the topics you care about. You'll have heard the prominent perspectives. You'll be that person who knows their shit. 

(Throw in mental model practice at work for good measure, and you'll be on your way to becoming a noticeably brighter person.)

But, to have productive debates with your friends, you'll first need to learn how to actually have a debate! Let's dive in.

How to debate

The argument framework

As a reminder, when someone presents an argument, consider using this framework to the extent you're interested in ensuring their reasoning is sound. In short, you want to sanity check their evidence, premises, and conclusion:

  1. Ask them to clearly state their conclusion.
  2. Ask what premises ("reasons") lead to their conclusion.
  3. Ask what evidence they have to support their reasons.
  4. Check their conclusion against the ten fallacies. Refute any fallacies that exist.
  5. If the argument still seems fishy, check their evidence against the three biases. Point out any that exist. Explain that any premises built on these biases must be re-examined.
"The body protects the brain. Skepticism protects the mind."
‚Äď Richard Dawkins

Your goals

Good debates share the goal of getting at least one party closer to the truth. That includes you too. Don't just look for opportunities to reaffirm your position. 

You must be ready to disavow your conclusion the moment you're proven wrong. Keep your ego small. Never double-down and cling to your emotional attachment.

Consider how the only debates Elon wants to have with you are about his mistakes:

I've hardcoded beginning and end times. Just hit play and let it run until it pauses.

The second goal all good debates share is developing a mutual understanding of why each party thinks the way they do. This is how you'll improve your arguing technique.

To help accomplish these two goals, let's conclude by learning The Rules of Debating.

"The truth will set you free, but first it will piss you off."
‚Äď Gloria Steinem

The rules

When debating another student of critical thinking, consider these rules:

You don't have to state these upfront, but whenever one is violated, kindly point it out.

(As always, these rules are included in the cheat sheet for easy referencing.)

One of the above rules is worth discussing further: Speaking slowly. 

Speaking slowly

Many people argue quickly. Either because their adrenaline is pumping or they think the quicker they speak, the more authoritative they'll sound. 

Or, worse, sometimes they'll talk fast because it lets them slip in dubious conclusions among their sound ones. They know that their speed makes it hard for opponents to critically assess everything they're saying. 

This is a conman's tactic. 

So point out whenever someone is talking too quickly. Kindly ask them to slow down: If they have confidence in their arguments, they will let each one be carefully assessed.

Example debate

Here's an example of a reasonable debate. See if you can spot any rules being broken:

(No, I am not the Ben Shapiro in that video. I am Julian Shapiro.)

ūü§Ē If you want more friends who can debate¬†toe-to-toe with you, share this guide with them:¬† If you record a¬†great¬†conversation and you obtain consent from both parties to publish it,¬†tweet me¬†a link to it so I can feature it!

Want to learn more?

This guide does not purport to teach you the entirety of critical thinking. The parts it does teach (fallacies, biases, and models) are themselves not taught in their entirety. 

Instead, I gave you the 80/20 ‚ÄĒ what you need to know to get going.

If you'd like to continue your learning, check out these really good books:

This handbook was not inspired by these books, so they're mostly all-new material!

ūü§Ē If you like how I wrote this guide, you might like the¬†Build¬†Muscle¬†handbook too.

‚ÄĒ Julian Shapiro

If you'd like to thank me for this handbook ūüėć

The best thanks I get is when you share this with friends and coworkers. I spent hundreds of hours writing this. And I'm giving it away for free.

If you like the insights I've shared and the resources I've put together, please share the handbook with a friend who could benefit from it.

Cheat sheet

If you enter your email below, the cheat sheet is automatically emailed to you so you can easily reference it in your inbox. You'll also be notified when my next guide is out.

If you liked the quality of this guide and want to learn how to play piano, how to write fiction, or how to speak Chinese, get excited because I'm releasing those guides next.

Thinking critically




Critical thinkers create their own models as needed: Watch for the complex tasks you routinely encounter. Identify commonalities among their solutions so you can work backwards to develop frameworks to convert data into similar solutions.

Real-world discussion

ūü§Ē Interesting in building muscle?¬†Check out my¬†Muscle Guide.