← All writing Final · Sep 2026

Thinking About Thinking

A small failure at a climbing gym, and what it taught me about thinking. Fast and slow thinking, the galaxy-brain trap that catches trained minds, and why the best guard for a powerful mind is the belief that we're all fallible.

Introduction

A few weeks ago, at a climbing gym, I asked the young man behind the counter how many customers they saw in a day. He was new and didn’t know. Then, in front of him, I turned to my daughter and told her she should strive to be someone who understands the big picture.

It was a small jab, and everyone felt it. I was implying that he didn’t know, or didn’t care about, the numbers his paycheck depends on. My daughter was embarrassed, for herself and for him, and later she told me so. She was right.

One of the ethics I hold is to be kind and leave people better than I found them. In that moment I did the opposite. I used a stranger as a teaching prop to make a point to my own child.

Later, I apologized to my family in a long text. This essay grew out of that text, because the mistake I made is the subject I care about most: how we think, how we train our thinking, and how the very habits that make us better thinkers can quietly make us worse.

1. Two Systems, Fast and Slow

Daniel Kahneman described the mind as running on two modes. System 1 is fast, automatic, and effortless. It recognizes a face, finishes a familiar sentence, and senses danger before you know why. System 2 is slow, deliberate, and effortful. It does long division, weighs evidence, and notices when a first impression is wrong.

System 1 is always on and always first. It hands System 2 a finished impression, and System 2, which Kahneman calls lazy, usually signs off without checking. We can call System 2 into action, but it costs effort, so most of the time we don’t.

The two systems are trained differently:

System 1 is trained by experience and repetition. Sports, games, humor, conversation, and ordinary life all build it. It gives us intuition, and it trains itself whether we mean it to or not.
System 2 is trained by slowing down on purpose. Reading, studying, writing, and working hard problems build it. It gives us accuracy, and it trains only when we make ourselves do the work.

2. Why I’ve Spent My Life Training System 2

I have spent most of my life deliberately training the slow system, because the fast one is so confidently wrong so often. Philip Tetlock puts it plainly in Superforecasting: “I realize I am rocking no one’s mental universe by saying that people often jump to judgment,” and “no one is immune.”

No one is immune. That includes me, and it includes the experts.

The reward for this training is hard to overstate. Slow thinking opens a kind of inner sight. You begin to see structure, connection, and beauty that were invisible before. There are mornings when the ideas moving through my head are so beautiful that I am moved to tears. It is hard work, and it is worth many wasted hours of hard labor to find those rare insights that make your soul sing.

3. Galaxy Brain: When the Slow System Goes Wrong

Here is the trap. Training System 2 makes you better at reasoning, and reasoning is a tool. A tool can be used for good or evil, and reasoning can just as easily defend conclusions you reached for other reasons.

Vitalik Buterin, the co-founder of Ethereum, names this problem well:

One important property for a style of thinking and argumentation to have is what I call galaxy brain resistance: how difficult is it to abuse that style of thinking to argue for pretty much whatever you want — something that you already decided elsewhere for other reasons? The spirit here is similar to falsifiability in science: if your arguments can justify anything, then your arguments imply nothing.

The galaxy brain is System 2 serving System 1. The fast mind picks an answer, and the slow mind builds the case. The more trained your slow mind is, the more impressive the case, and the harder it is to see that the verdict came first.

That is what happened at the gym. The lesson I gave my daughter was a good one: understanding the big picture matters. But the lesson wasn’t why I said it. A quick judgment about a new employee came first, and my slow mind dressed it up as mentorship. A true principle, well argued, was carrying an unkind impulse. My daughter’s System 1, reading the room, was more accurate than my System 2.

The lesson was also incomplete. I didn’t bother to explain Goodhart’s Law: when a measure becomes a target, it stops being a good measure. A new employee chasing a daily customer count could easily make things worse. The better lesson is to focus on what drives the number, such as customer service and sales techniques. My quick judgment skipped the part of the lesson that would have actually helped him.

4. Fallibilism: What Checks the Checker

If System 2 checks System 1, what checks System 2? More thinking, but of a particular kind: thinking that acknowledges its own fallibility. The name for this is fallibilism: the view, developed most fully by Karl Popper and David Deutsch, that any of our knowledge might be mistaken. Even the regularities we rely on can be wrong or can change. We make progress by finding and fixing errors, not by proving we are right.

Fallibilism turns galaxy-brain resistance from a property of arguments into a habit of mind. A few practices that follow from it:

Ask what would change your mind. If nothing could, you aren’t reasoning. You are defending.
Notice when the conclusion arrived before the argument. A case that feels too elegant, built too fast, is a warning sign.
Invite criticism from outside your head. Other people, especially people who see differently, catch errors you can’t. My daughter caught mine.
Hold even your best ideas with an open hand. The ideas I love most are the ones I most need to test.

The point isn’t to trust your slow mind less. It is to aim it at itself: to treat your own reasoning as one more conjecture waiting to be criticized.

Conclusion: Live Fully in Both

When I wrote to my family, I told them that System 2 would elevate them above their peers. I stand by that, though it needs a word of explanation. It isn’t a contest. Most people never do the slow, hard work of training this system, so those who do gain things others won’t: clearer sight, better judgment, and a deep, quiet joy. Rising is a side effect of growing, not the goal. And among the most valuable of those gains is the ability to see when you are wrong.

So here is what I hope for my kids, and for anyone who reads this. Train the slow mind. Read hard books, write, and stay with difficult problems until they open. Guard that mind with fallibilism, so its power serves the truth and not your ego. And don’t neglect the fast mind. Play games, laugh, keep good friends, and read the room.

Life is for living fully in both systems. As you pursue greatness, the best thing you can do is carry the belief that we’re all fallible.