first-principles-thinking
Concept Card
What it is: First-principles thinking is a reasoning discipline that breaks a problem down to propositions, definitions, constraints, and values that cannot be derived from deeper premises inside the relevant domain, then rebuilds a solution from those primitives. Richard Feynman's governing axiom — "the first principle is that you must not fool yourself, and you are the easiest person to fool" — captures the epistemic core: the method is a defense against self-deception disguised as reasoning.
Mental model: Treat every accepted belief as a candidate, not a foundation. Sort candidates into observed facts, definitions, constraints, conventions, analogies, preferences, and derived claims. Keep only the load-bearing primitives, then derive the answer upward with explicit warrants.
Why it exists: It prevents inherited assumptions from masquerading as laws. Many bad solutions persist because a team copied a pattern, optimized a proxy, or accepted an old constraint without asking whether it was still load-bearing.
What it is NOT: It is not root-cause analysis after a failure, not inversion, not Bayesian updating, not expected-value scoring, not second-order reasoning about downstream consequences, and not an excuse to discard useful prior art.
Adjacent concepts: epistemic-grounding, Toulmin argument, DSRP systems thinking, conceptual modeling, inversion, Bayesian reasoning, expected value, second-order thinking, Chesterton's Fence, the Einstellung effect, functional fixedness, CAP-style structural limits.
One-line analogy: It is dismantling a problem to the structural beams, then rebuilding only what those beams can actually support.
Common misconception: The trap is thinking "from scratch" means "ignore history." History is evidence; first principles decide whether that evidence represents a primitive, a derived claim, or a stale convention.