Part 1 · 2 chapters · ~12 min

Mental Models Worth Owning

First principles, inversion, second-order effects, opportunity cost, base rates and the outside view, margin of safety, Occam's razor and Hanlon's razor, map versus territory, and using a few models well rather than collecting many.

3

Six models

Charlie Munger's advice was to hold a latticework of models from many fields. The practical version: know a handful deeply and reach for them deliberately in design reviews and planning.

MENTAL MODELS WORTH OWNING
a small set that pays off every week
first principlesBreak a problem into fundamentalsyou know are true, then reason upinstead of copying.inversionAsk how to guarantee failure, thenavoid those things. Premortems areinversion.second-order effectsAsk "and then what?" twice.Consequences of consequencesdecide outcomes.opportunity costEvery yes is a no to the next bestthing. Compare against that, notnothing.base ratesStart from how often things likethis usually happen, then adjustfor specifics.margin of safetyLeave room for being wrong:capacity, money, time, scope.
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first principles
Instead of "competitors use microservices, so should we", ask what is fundamentally true: we have 6 engineers, one domain, and deploy pain from a slow test suite. That points to fixing tests, not splitting services.
reason up from what is truenot by analogy to others
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A few more, briefly

modelin one line
map is not the territorythe dashboard, the diagram and the plan are models; reality is messier
Occam's razorprefer the simpler explanation that fits all the facts (the deploy, not a cosmic ray)
Hanlon's razordo not attribute to malice what is explained by missing information or a hard situation
Chesterton's fencebefore removing something whose purpose you do not know, find out why it was put there
Goodhart's lawa measure that becomes a target stops measuring well