First Principles Thinking

Origin. Aristotle's ἀρχαί; Descartes' method of doubt; contemporary usage via engineering culture.

Mechanism. Decomposes a claim into propositions that are held on their own evidence rather than by inheritance, then reconstructs upward. Reasoning by analogy propagates whatever error is in the source; reasoning from first principles does not, at the cost of much more work.

Procedure. List everything believed about the problem. For each item, ask by what evidence it is held. Discard inherited items. Rebuild the conclusion using only the remainder. Note explicitly where the rebuild fails to reach the original conclusion.

Applies to. Cost structures, physical limits, and any domain where an industry consensus has ossified around a contingent historical fact.

Limitations. Applied to domains where the 'primitives' are themselves theory-laden, it produces confident error. There is no floor of self-evident propositions in most social and linguistic domains.