First principles thinking, which is sometimes called reasoning from first principles, is one of the most effective strategies you can employ for breaking down complicated problems and generating original solutions. It also might be the single best approach to learn how to think for yourself.
The first principles approach has been used by many great thinkers including inventor Johannes Gutenberg, military strategist John Boyd, and the ancient philosopher Aristotle, but no one embodies the philosophy of first principles thinking more effectively than entrepreneur Elon Musk.
In 2002, Musk began his quest to send the first rocket to Mars — an idea that would eventually become the aerospace company SpaceX.
He ran into a major challenge right off the bat. After visiting a number of aerospace manufacturers around the world, Musk discovered the cost of purchasing a rocket was astronomical — up to $65 million. Given the high price, he began to rethink the problem. 
“I tend to approach things from a physics framework,” Musk said in an interview. “Physics teaches you to reason from first principles rather than by analogy. So I said, okay, let’s look at the first principles. What is a rocket made of? Aerospace-grade aluminum alloys, plus some titanium, copper, and carbon fiber. Then I asked, what is the value of those materials on the commodity market? It turned out that the materials cost of a rocket was around two percent of the typical price.” 
Instead of buying a finished rocket for tens of millions, Musk decided to create his own company, purchase the raw materials for cheap, and build the rockets himself. SpaceX was born.
Within a few years, SpaceX had cut the price of launching a rocket by nearly 10x while still making a profit. Musk used first principles thinking to break the situation down to the fundamentals, bypass the high prices of the aerospace industry, and create a more effective solution. 
First principles thinking is the act of boiling a process down to the fundamental parts that you know are true and building up from there. Let’s discuss how you can utilize first principles thinking in your life and work.
Defining First Principles Thinking
A first principle is a basic assumption that cannot be deduced any further. Over two thousand years ago, Aristotle defined a first principle as “the first basis from which a thing is known.” 
First principles thinking is a fancy way of saying “think like a scientist.” Scientists don’t assume anything. They start with questions like, What are we absolutely sure is true? What has been proven?
In theory, first principles thinking requires you to dig deeper and deeper until you are left with only the foundational truths of a situation. Rene Descartes, the French philosopher and scientist, embraced this approach with a method now called Cartesian Doubt in which he would “systematically doubt everything he could possibly doubt until he was left with what he saw as purely indubitable truths.” 
In practice, you don’t have to simplify every problem down to the atomic level to get the benefits of first principles thinking. You just need to go one or two levels deeper than most people. Different solutions present themselves at different layers of abstraction. John Boyd, the famous fighter pilot and military strategist, created the following thought experiment which showcases how to use first principles thinking in a practical way. 
Imagine you have three things:
- A motorboat with a skier behind it
- A military tank
- A bicycle
Now, let’s break these items down into their constituent parts:
- Motorboat: motor, the hull of a boat, and a pair of skis.
- Tank: metal treads, steel armor plates, and a gun.
- Bicycle: handlebars, wheels, gears, and a seat.
What can you create from these individual parts? One option is to make a snowmobile by combining the handlebars and seat from the bike, the metal treads from the tank, and the motor and skis from the boat.
This is the process of first principles thinking in a nutshell. It is a cycle of breaking a situation down into the core pieces and then putting them all back together in a more effective way. Deconstruct then reconstruct.
How First Principles Drive Innovation
The snowmobile example also highlights another hallmark of first principles thinking, which is the combination of ideas from seemingly unrelated fields. A tank and a bicycle appear to have nothing in common, but pieces of a tank and a bicycle can be combined to develop innovations like a snowmobile.
Many of the most groundbreaking ideas in history have been a result of boiling things down to the first principles and then substituting a more effective solution for one of the key parts.
For instance, Johannes Gutenberg combined the technology of a screw press — a device used for making wine — with movable type, paper, and ink to create the printing press. Movable type had been used for centuries, but Gutenberg was the first person to consider the constituent parts of the process and adapt technology from an entirely different field to make printing far more efficient. The result was a world-changing innovation and the widespread distribution of information for the first time in history. 
The best solution is not where everyone is already looking.
First principles thinking helps you to cobble together information from different disciplines to create new ideas and innovations. You start by getting to the facts. Once you have a foundation of facts, you can make a plan to improve each little piece. This process naturally leads to exploring widely for better substitutes.
The Challenge of Reasoning From First Principles
First principles thinking can be easy to describe, but quite difficult to practice. One of the primary obstacles to first principles thinking is our tendency to optimize form rather than function. The story of the suitcase provides a perfect example.
In ancient Rome, soldiers used leather messenger bags and satchels to carry food while riding across the countryside. At the same time, the Romans had many vehicles with wheels like chariots, carriages, and wagons. And yet, for thousands of years, nobody thought to combine the bag and the wheel. The first rolling suitcase wasn’t invented until 1970 when Bernard Sadow was hauling his luggage through an airport and saw a worker rolling a heavy machine on a wheeled skid. 
Throughout the 1800s and 1900s, leather bags were specialized for particular uses — backpacks for school, rucksacks for hiking, suitcases for travel. Zippers were added to bags in 1938. Nylon backpacks were first sold in 1967. Despite these improvements, the form of the bag remained largely the same. Innovators spent all of their time making slight iterations on the same theme.
What looks like innovation is often an iteration of previous forms rather than an improvement of the core function. While everyone else was focused on how to build a better bag (form), Sadow considered how to store and move things more efficiently (function).
How to Think for Yourself
The human tendency for imitation is a common roadblock to first principles thinking. When most people envision the future, they project the current formforward rather than projecting the function forward and abandoning the form.
For instance, when criticizing technological progress some people ask, “Where are the flying cars?”
Here’s the thing: We have flying cars. They’re called airplanes. People who ask this question are so focused on form (a flying object that looks like a car) that they overlook the function (transportation by flight).  This is what Elon Musk is referring to when he says that people often “live life by analogy.”
Be wary of the ideas you inherit. Old conventions and previous forms are often accepted without question and, once accepted, they set a boundary around creativity. 
This difference is one of the key distinctions between continuous improvement and first principles thinking. Continuous improvement tends to occur within the boundary set by the original vision. By comparison, first principles thinking requires you to abandon your allegiance to previous forms and put the function front and center. What are you trying to accomplish? What is the functional outcome you are looking to achieve?
Optimize the function. Ignore the form. This is how you learn to think for yourself.
The Power of First Principles
Ironically, perhaps the best way to develop cutting-edge ideas is to start by breaking things down to the fundamentals. Even if you aren’t trying to develop innovative ideas, understanding the first principles of your field is a smart use of your time. Without a firm grasp of the basics, there is little chance of mastering the details that make the difference at elite levels of competition.
Every innovation, including the most groundbreaking ones, requires a long period of iteration and improvement. The company at the beginning of this article, SpaceX, ran many simulations, made thousands of adjustments, and required multiple trials before they figured out how to build an affordable and reusable rocket.
First principles thinking does not remove the need for continuous improvement, but it does alter the direction of improvement. Without reasoning by first principles, you spend your time making small improvements to a bicycle rather than a snowmobile. First principles thinking sets you on a different trajectory.
If you want to enhance an existing process or belief, continuous improvement is a great option. If you want to learn how to think for yourself, reasoning from first principles is one of the best ways to do it.