── ── Mental model

Feynman Technique

The Feynman Technique tests whether understanding is genuine (can reproduce, predict, extend) or surface (can recognize, recall jargon). It exploits a cognitive asymmetry: recognizing an explanation is much easier than reproducing it. Feynman's principle: "The first principle is that you must not fool yourself — and you are the easiest person to fool."

How it works

Four steps producing a Feynman Understanding Audit. Stop rule: complete when explanation is genuinely plain — not when jargon is replaced with different jargon. If you cannot simplify further without factual loss, name the irreducible core.

1. Choose the concept and write its name. One specific concept, not a topic. "Compounding interest" is a concept. "Finance" is not. 2. Produce a plain-language explanation. As if to a curious 12-year-old: no jargon without definition, no circular definitions, no hedges. Record verbatim — do not edit in real time. 3. Diagnose the gaps. Mark every: (a) undefined technical term; (b) circular definition; (c) "it's complicated" hedge; (d) prediction that doesn't match reality. For each gap: name the specific question you cannot answer. Return to primary sources. 4. Simplify and refine. Rewrite incorporating what you learned. Test each analogy: does it break down where the original concept breaks down? If not, replace it.

When to use it

• user says 'explain this simply', 'teach me like I'm five', 'do I really understand this', 'what's the simplest way to think about X', 'what's missing in my model', wants to test genuine vs. surface understanding of a concept, or is preparing to teach/present and needs to verify their mental model

Worked example

Feynman and the Challenger O-Ring Investigation (1986)

Primary-source-documented case. The Presidential Commission on the Space Shuttle Challenger Accident (the Rogers Commission) was convened in February 1986 following the January 28 disaster. Feynman's participation is documented in his own account in What Do You Know? and the Commission's formal record.