CODEXCard 1 of 12 · 12 Mental Models
Inversion mental model
Solve it backwards.
The inversion mental model is the habit of turning a question around. Rather than asking how to achieve a goal, you ask what would make it impossible. Munger often borrowed advice he credited to the mathematician Carl Jacobi, invert, always invert, and joked that he only wanted to know where he would die so he could avoid going there.
It works because failure is usually easier to describe than success. Ask how to have a good marriage and the answers are vague. Ask how to ruin one and you get a sharp list: dishonesty, contempt, neglect. Mathematicians use the same move, proving something by showing what follows if it were false. Removing the obvious ways to fail often leaves you close to a good answer.
The common mistake is treating inversion as a party trick for occasional hard problems. Its value comes from repetition. Applied to every important decision, it becomes a quiet safety check that catches errors forward thinking misses. Used once and forgotten, it changes little.
Inversion connects closely to Munger's advice to avoid standard stupidity. Both rest on the same insight: steadily avoiding big mistakes often beats chasing brilliant moves. It also works as a check on confirmation bias, since it forces you to look at how you might be wrong.
Example
You want your weekly team meeting to be useful. Instead of brainstorming improvements, you list what would make it a guaranteed waste: no agenda, too many people, decisions never recorded, running over time. Fixing those four things takes ten minutes and improves the meeting more than any clever new format.
Try it this week
For one goal this week, write down five ways you could guarantee failure, then remove the one you are closest to doing.
From 12 Mental Models (Charles T. Munger · 1995).
