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name: first-principles-thinking description: A mental model for breaking down basic truths to generate original solutions. Use for innovation, novel problems, or when stuck in conventional thinking. license: MIT metadata: type: mental-model version: "1.0"

First Principles Thinking

Overview

First Principles Thinking is a mode of inquiry that relentlessly questions assumptions to get to the fundamental truth of a problem, then builds a solution from scratch. It is the tool of the innovator, used to bypass "reasoning by analogy" (copying what others do).

When to Use This Skill

• Innovation: When the user wants to invent a new way of doing things.
• Stuck Points: When standard solutions are too expensive, too slow, or impossible.
• Debugging: When "it should work" but doesn't—strip away assumptions about why it should work.
• Cost Analysis: When you need to understand the absolute floor of a cost structure.

Methodology

1. Identify & Question Assumptions (Socratic Method)

Goal: Expose the hidden beliefs limiting the current view.

• Prompt: "What are we assuming to be true here? Why do we think that?"
• Technique: Ask "Why?" 5 times.
  • CRITICAL: Do not answer from memory. Search/Read to verify the answer to each "Why?".
  • Stop: When you hit a physical law, a mathematical truth, or a verified hard constraint.

2. Deconstruct to Constituent Parts

Goal: Find the atomic units that cannot be reduced further.

• Action: Break the system down into:
  • Physics: Mass, energy, material properties.
  • Logic: Axioms and necessary truths.
  • Economics: Raw material costs, time units.

3. Reconstruct from Scratch

Goal: Build a 10x better solution using only the essential parts.

• Action: Ignore "how it's usually done." Combine the atomic units in the most efficient way possible to achieve the goal.

Examples

The SpaceX Example (Cost Reduction)

User: "Rockets are too expensive." Analogy Reasoning: "Rockets define the market price. We can maybe save 10% by negotiating." First Principles Reasoning: "A rocket is just aluminum, titanium, and fuel. The spot price of these materials is 2% of a rocket's cost. The cost is inefficient manufacturing. We will buy raw metal and build it ourselves."

The "Chef vs. Cook"

Analogy (Cook): Follows a recipe. If an ingredient is missing, they stop. First Principles (Chef): Understands why the acid balances the fat. If a lemon is missing, they use vinegar, because the principle is acidity.

Resources

• Detailed Research Notes