First Principles Thinking

---
name: first-principles-thinking
description: Use first-principles thinking as a tool for any question, design problem, strategy, decision, or explanation where the user wants to reason from fundamentals instead of analogy, convention, or inherited assumptions.
---

# First-Principles Thinking

Use this skill when a question would benefit from stripping away assumptions and rebuilding the answer from fundamentals.

## Purpose

First-principles thinking decomposes a problem into the most basic truths, constraints, mechanisms, or goals that are hard to reduce further. It is useful when conventional answers may be stale, copied, cargo-culted, or overly constrained by analogy.

## Procedure

1. State the question or problem plainly.
2. List the current assumptions, conventions, analogies, or inherited defaults.
3. Separate what must be true from what is merely customary.
4. Identify the irreducible fundamentals:
   - physical constraints
   - economic constraints
   - human needs or incentives
   - technical primitives
   - logical requirements
   - legal or ethical boundaries
5. Rebuild possible answers from those fundamentals.
6. Compare the rebuilt answer against the conventional answer.
7. Name the practical implication, tradeoff, or experiment.

## Output format

Use this concise structure unless the user asks otherwise:

```markdown
## Problem
...

## Assumptions to question
- ...

## First principles
- ...

## Rebuilt answer
...

## Difference from the default answer
...

## Practical next step
- ...
```

## Guardrails

- Do not confuse "first principles" with contrarianism; sometimes the conventional answer is correct.
- Do not reduce away human, social, legal, or ethical constraints when they are fundamental to the problem.
- State uncertainty clearly when a supposed principle is actually an empirical claim.
- Prefer useful decomposition over theatrical reduction.

## Canonical questions

Best when the conventional answer might be cargo-culted and the fundamentals are checkable:

- "Why do batteries cost what they cost — what's the floor?"
- "Does our company actually need a sales team?"
- "What would education look like if we designed it today from scratch?"
- "Is a 30-year mortgage actually the right structure for home financing?"
- "Why do meetings default to 30 or 60 minutes?"

Poor fits: questions where convention *is* the answer (etiquette, coordination standards like which side of the road to drive on), or where the fundamentals are unknowable.