First Principles

Most thinking is analogical. You look at how something was done before and do it similarly. You take existing solutions and apply them to new problems.

This works most of the time. It’s efficient. But it also inherits all the assumptions and limitations of previous approaches.

First principles thinking is different. You break a problem down to its fundamental truths - the things that are definitely true - and reason up from there.

Why analogical thinking has limits

Analogical thinking works by pattern-matching:

“How was this done before?”
“What do experts in the field do?”
“What’s the industry standard?”

This is useful because:

You don’t reinvent the wheel
You learn from others’ experience
You avoid basic mistakes

But it’s limiting because:

You inherit others’ assumptions
You’re bounded by their imagination
You can’t see solutions outside the pattern

If everyone thinks analogically, everyone gets similar results. Breakthrough thinking requires breaking patterns.

First principles in practice

First principles thinking asks:

“What do we know for sure?”
“What are the fundamental constraints?”
“What’s actually true, vs. what we assume is true?”

Then you build up from those foundations, ignoring how things have been done before.

Classic example: SpaceX

The space industry believed rockets were expensive because… rockets are expensive. That’s how it had always been.

Elon Musk asked: what are rockets made of? Aluminum, titanium, carbon fiber. What do those materials cost? Much less than a finished rocket costs.

First principles revealed that the materials weren’t expensive - the manufacturing and supply chain were. So SpaceX redesigned manufacturing from scratch, building rockets for a fraction of traditional costs.

They didn’t accept “rockets are expensive” as a fundamental truth. They questioned it.

How to apply first principles

1. Identify the problem clearly

What exactly are you trying to solve? Be specific.

Fuzzy problems get fuzzy solutions. Clear problems can be decomposed.

2. Question assumptions

Take everything you “know” about the problem and ask: is this actually true? Or is it just assumed?

Useful prompts:

“Why do we think this?”
“What if the opposite were true?”
“Is this a law of physics or just convention?”
“Who said this was a constraint?”

Many “constraints” are actually just “how things have been done.”

3. Identify fundamental truths

What remains after you strip away assumptions? What is definitely, undeniably true?

These are your first principles - the foundation you’ll build from.

For physics problems, these might be actual physical laws. For social problems, these might be basic human needs. For business problems, these might be core economics.

4. Build up from the foundation

Starting only from first principles, reason toward a solution.

Don’t reference existing approaches. Build fresh. What would you do if you were solving this for the first time?

5. Compare with conventional approach

Now look at how the problem is usually solved. How does your first-principles solution differ? Is the difference meaningful?

Sometimes you’ll end up at the same place - the conventional approach was actually optimal. But often you’ll find new possibilities.

When to use it (and when not to)

First principles thinking is powerful but expensive. It requires time, effort, and often expertise.

Use it when:

The stakes are high
Conventional approaches aren’t working
You want breakthrough innovation
You’re in a new domain without precedent
Something feels wrong but you can’t articulate why

Don’t use it when:

The problem is routine
Time is limited
Best practices work fine
You lack domain knowledge to identify first principles

Most daily decisions don’t need first principles thinking. But a few important ones do.

Common pitfalls

False fundamentals. You think you’ve reached a first principle, but it’s actually an assumption. Keep asking “why?” and “is this really true?”

Analysis paralysis. You can always dig deeper. At some point you have to stop and build. Perfect foundations don’t exist.

Ignoring evidence. First principles doesn’t mean ignoring empirical data. If something has worked before, that’s information - just not a constraint.

Overcomplication. Sometimes the simple, conventional answer is right. First principles shouldn’t make things harder than necessary.

Ego. “I figured it out from first principles” can become a way of dismissing accumulated wisdom. Humility is still required.

Applied to life decisions

First principles isn’t just for business or engineering. You can apply it to life:

Career: “What do I need from work?” → money, meaning, growth, flexibility. Strip away prestige, expectations, “should.” What actually matters to you?

Relationships: “What do I want from relationships?” → connection, support, growth, fun. Not what society says relationships should be. What do you actually need?

Lifestyle: “What do I need to live well?” → shelter, food, safety, connection, purpose. Question every assumption about what a “good life” requires.

Most life decisions are made analogically - “this is what people do.” First principles asks: “but what do I actually need?”

The deeper skill

First principles is really about intellectual courage - the willingness to question everything, including things everyone “knows.”

Most people don’t do this because:

It’s uncomfortable
It risks looking stupid
It challenges authority
It’s hard

But it’s also how breakthrough thinking happens. The ability to ask “but is that actually true?” when everyone else assumes it is.

You don’t need to use first principles for everything. But having it as a tool - knowing you can question anything, decompose any problem, rebuild from scratch - that’s power.

Related: Problem-Solving (other approaches to getting unstuck), Cognitive Biases (why assumptions persist), Learning (understanding deeply)