First Principles thinking, with examples

First principles thinking is the practice of decomposing a problem into the underlying truths that can't be reduced further, then reasoning up from those truths instead of from analogies to other situations. The promise is that you arrive at conclusions that pure analogical thinking — "this is like X, so do Y" — can't reach, because analogies inherit other people's assumptions.

The idea is old (Aristotle named it; René Descartes formalized it). The modern fashion for it traces to Elon Musk's frequent retelling of how SpaceX brought launch costs down by refusing to accept that rockets had to cost what existing rockets cost.

Why analogical thinking dominates

Most decisions, most of the time, run on analogy: we hire like other companies hire, we price like the competitor prices, we structure the team like the last team we worked on. Analogy is cheap. It works because most problems aren't new — and applying a known solution is faster than re-deriving one from scratch.

The cost is that you inherit assumptions baked into the analogy. If the original team had three founders and you have one, the structure won't fit. If your competitor's pricing is anchored to a customer profile that doesn't match yours, copying it will mis-price you. The errors are silent.

First principles thinking is what you reach for when the cost of inherited assumptions is high enough that re-deriving is worth the effort. That's not every decision — it's a specific kind.

How to actually do it

The process is three steps, and the third is the one most people skip.

1. State the problem in your own words. Write down what you're trying to figure out. If you can't write a single sentence, you don't know the problem well enough yet.
2. Decompose into atomic statements. Break the problem into its components. Keep asking "is this really true, or is it true because someone said it is?" Keep going until you hit something verifiable — a physical law, a measurable cost, a logically necessary truth.
3. Reason back up from the atoms. Now construct your own answer using only the atoms, without re-importing the original framing. This step is where most people fail — they reach an atom, get tired, and just relax back into the original analogical answer.

Two worked examples

Example 1: rocket costs (SpaceX)

The analogical answer: rockets are expensive because rockets are expensive. The market price for putting a kilogram into orbit was $20,000+, and competitors all priced near that.

First principles decomposition: what is a rocket physically made of? Aluminum alloys, titanium, copper, carbon fiber, fuel. What do those raw materials cost on the commodities market? Approximately 2% of the finished rocket's price.

The atomic truth: the bill of materials does not justify the finished price. The rest is engineering, manufacturing, and historical institutional decisions — all of which are in principle changeable. SpaceX's whole strategy is built on operating in the 98% gap between raw material cost and market price.

The reasoning is not magic; it's just the discipline of refusing the inherited answer.

Example 2: a pricing decision (mundane)

Imagine you're a SaaS founder pricing a product. The analogical answer: look at three competitors, pick the middle price, maybe knock 10% off because you're new.

First principles decomposition: what does the buyer actually save (or earn) per month when they use your product? What's the cost to deliver it? What's the lowest price at which you can survive long enough to learn whether the product works? What's the highest price the buyer would pay before substituting back to spreadsheets?

You may end up at a similar number to the competitor anyway. Or you may end up at 3× the competitor's price, because the value you're capturing for the buyer is genuinely larger and the competitor is the one who mis-priced. Either way, you arrived at a number you can defend, and you'll know what to do when a competitor changes their price.

The trap

The trap is that first principles thinking is expensive, and most people apply it to problems that don't deserve the cost. You don't need to reason from first principles about whether to buy croissants or scones. You barely need it for what color the homepage button should be. The discipline is to identify which 5% of decisions are worth the cost — usually decisions that are hard to reverse, large in dollar terms, or strategically defining — and reserve first principles thinking for those.

Apply it to everything and you'll be slow and exhausted. Apply it to nothing and you'll be a fast-moving competitor of average ideas.

When first principles isn't the right tool

• For triage, use the Eisenhower Matrix. First principles on every email is paralysis.
• For prioritization across many comparable options, use RICE. First principles on each backlog item is overkill.
• When you don't yet know the problem well enough, talk to customers first. First principles thinking on the wrong question produces a beautifully-reasoned wrong answer.

How to practice

Pick one decision you already made by analogy this quarter. Run it again from first principles. Compare the two answers. The point is not to redo the decision; it's to build the muscle of recognizing which 5% of decisions deserve the treatment.

Related frameworks

• Inversion — the mirror discipline: reason from the failure case backwards
• 5 Whys — a lightweight tool for decomposing a single observation
• Premortem — first-principles risk analysis
• Decision tree — structured way to map the consequences once you've reached your atomic truths

Want to walk through a decision this way? Start a canvas → and use the First Principles framework template.