First Principles

Break problems down to fundamental truths and reason up from there.

The Core Idea

First principles thinking is the practice of questioning every assumption about a problem until you reach the foundational truths that cannot be further reduced. From these bedrock facts, you rebuild solutions from the ground up.

Key Principles

Strip Away Assumptions Most of what we “know” is just convention, analogy, or tradition. First principles thinking demands you question everything until you hit immutable facts.

Rebuild From Scratch Once you’ve identified the fundamental truths, reconstruct your understanding without the baggage of how things “should” work.

Physics Over Convention Focus on the laws of nature and mathematics rather than what competitors do or what’s been done before.

Applications

Problem Solving When stuck, strip the problem to its core elements. What do you actually know to be true? What are you assuming?

Innovation Revolutionary products come from reasoning up from first principles rather than iterating on existing solutions.

Learning Master subjects by understanding the foundational concepts, not memorizing facts and procedures.

Decision Making Challenge your own beliefs and inherited wisdom. What do you believe because you’ve verified it vs. what you believe because others told you?

The Process

1. Identify the problem - Clearly state what you’re trying to solve
2. Question assumptions - List everything you think you know about it
3. Break down to fundamentals - Keep asking “why?” until you hit bedrock facts
4. Rebuild - Construct new solutions from these fundamental truths

Example: Elon Musk on Rockets

Traditional aerospace thinking: “Rockets are expensive because they’ve always been expensive.”

First principles approach:

• What are rockets made of? Aluminum alloys, titanium, copper, carbon fiber
• What do these materials cost on the commodity market? About 2% of the typical rocket price
• Fundamental truth: The raw materials are cheap, the manufacturing and assembly process is expensive
• Solution: Redesign manufacturing to reduce costs, eventually making reusable rockets

Working With First Principles

• Use when facing novel problems without clear precedents
• Apply when current solutions feel constraining or inefficient
• Be prepared for radical departures from convention
• Don’t use for every decision - it’s mentally taxing
• Combine with other models for richer understanding

Common Pitfalls

• Stopping before reaching true fundamentals
• Confusing widely held beliefs with fundamental truths
• Over-applying and wasting time on trivial decisions
• Ignoring practical constraints after the thought experiment

“I think it’s important to reason from first principles rather than by analogy. The normal way we conduct our lives is we reason by analogy… First principles is kind of a physics way of looking at the world.” - Elon Musk