Cognitive Scaffold

Preparing your thinking workspace

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MENTAL MODEL · M1987

Greenspun's Tenth Rule

Greenspun's Tenth Rule
SystemsHigh supportSystems Theory
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Version 1.0.0 · Updated 2026-07-30

CORE DEFINITION

“Any sufficiently complicated C or Fortran program contains an ad hoc, informally-specified, bug-ridden, slow implementation of half of Common Lisp.” -

SCAFFOLDING EFFECT

psychology

Reduce cognitive load

The ultimate form of system evolution. - Extended meaning: When a system (whether software or a rule system) becomes sufficiently complex, designers often have to reinvent a set of “scripting language” or “meta-rules” to patch it, but this newly invented set of rules is usually bad. This warns us: if we do not use a sufficiently flexible underlying architecture from the start, the patches made later for flexibility will be disastrous.

anchor

Anchor fast decisions

Greenspan's famous saying: 'Those who think they understand risk before a crisis hits will sooner or later be proven wrong.' It implies that the risks of complex systems cannot be fully captured by models.

MINIMUM ACTION

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Source support: Explicit

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    en.wikipedia.orghttps://en.wikipedia.org/wiki/Greenspun%27s_tenth_ruleZH · Explicit
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