For centuries, everyone knew that heavier objects fell faster than lighter ones. It was obvious. It was common sense. Aristotle said it was true, and for nearly 2,000 years, no one questioned it—until Galileo decided to check. By breaking down the problem to its fundamental truths and actually testing it, he discovered what we know now: in a vacuum, all objects fall at the same rate. One simple act of questioning an assumption changed our understanding of physics forever.
How do the extraordinary minds of our world continuously challenge what we think is impossible?
Take this quote from Charlie Munger, the billionaire investor and legendary thinker. He once said:
"I think it is undeniably true that the human brain must work in models. The trick is to have your brain work better than the other person's brain because it understands the most fundamental models, ones that will do most work per unit."
This week, we're diving into one of those "fundamental models" that can do the most work per unit: First Principles Thinking, which is coincidentally attributed to Aristotle.
What is First Principles Thinking?
First Principles Thinking is about boiling problems down to their core truths—the things that are undeniably true—and reasoning up from there. It's not about following what others have done before or accepting conventional wisdom - quite the opposite.
Consider Elon Musk's approach to building rockets. Everyone "knew" that only governments and massive aerospace corporations could possibly build them. That's just how it was. But instead of accepting these industry assumptions, Musk broke the problem down to its most basic elements: What are the raw materials needed for a rocket? What do they actually cost?
The answer was surprising: the raw materials for a rocket—primarily aluminum alloys, titanium, copper, and carbon fiber—only cost about 2% of the typical rocket price. This revelation led to a fundamental question: why were rockets so expensive? By challenging the conventional manufacturing process, vertical integration, and the assumption that rockets couldn't be reused, SpaceX managed to reduce launch costs by over 90%. They didn't just iterate on existing rocket designs—they reimagined the entire process from the ground up.
You were once a master of this…
Want to understand First Principles Thinking? Watch a child. When children reach that age of constantly asking "why," they're natural practitioners of First Principles Thinking. Why is the sky blue? Why do we go to work? Why does the Earth spin? They keep digging deeper until adults often resort to "because I said so"—this is the death of First Principles Thinking.
This childlike curiosity is a powerful tool for understanding the world and making better decisions. Nurture it.
Beyond Work: First Principles in Life
This thinking extends far beyond business. Take material desires, for instance. Why do you want that fancy car or expensive watch? For status? To look cool? Keep asking why.
Strip away the surface-level answers and you'll often find that what you really want is something far more fundamental: security in an uncertain world, the respect of your peers, the ability to provide for loved ones, or the freedom to make choices on your own terms. Sometimes, what looks like a desire for wealth or status is actually a deeper yearning for personal sovereignty—the ability to control your time, protect your health, and create opportunities for yourself and others.
By understanding these core desires, you might realize that the path forward isn't about acquiring things, but about becoming the kind of person who naturally attracts what you truly value: financial independence rather than flashy possessions, genuine relationships rather than surface-level admiration, and real impact rather than the appearance of success.
Channel Your Inner Child
Start asking "why". Don't accept surface-level answers or conventional wisdom. Whether you're tackling a business problem or examining your personal goals, keep digging until you reach the fundamental truth.
Remember: The path to fulfillment isn't about what you acquire, but who you become.
Coming Next Week
We've explored how breaking things down to First Principles brings clarity and focus. But what if, instead of focusing on what to do, you focused on what not to do? Next week, we'll dive into another powerful mental model from Charlie Munger's toolkit: Inversion. It might just change everything about how you approach problems, goals, and even relationships. Don't miss it!
If you want to learn about more mental models I highly recommend checking out Shane Parrish’s The Great Mental Models. There are four volumes, and I have loved every second spent reading them!