Man with a Hammer
"To a man with a hammer, everything looks like a nail." Charlie Munger uses this phrase constantly to warn against the danger of having only one mental model.
An economist sees every problem as an incentive problem. A programmer sees every problem as an automation problem. A lawyer sees every problem as a liability problem. Each is partly right — and dangerously incomplete.
The Antidote
The cure is Munger's Latticework of Mental Models: deliberately collect frameworks from many disciplines so you have more than one tool. When you catch yourself reaching for the same model every time, that's a signal to step back and ask what other lens might apply.
Connections
This concept is closely related to Circle of Competence — the hammer problem is what happens when someone operates confidently outside their circle using the only tool they know. Cognitive Biases catalogs many of the systematic errors that result from this kind of narrow thinking.
Inversion offers a practical check: instead of asking "how does my favorite model apply here?", ask "what would happen if my favorite model is completely wrong about this?"