Inversion
Jacobi gave his students one rule: man muss immer umkehren — invert, always invert. Stuck on a proof, turn it around. The path you can’t find forward is sometimes obvious in reverse. Munger picked the rule up two centuries later and pointed it at life. How do you build a happy marriage? Hard. What reliably destroys one? Contempt. Financial deceit. The slow erosion of small attentions noticed and not returned. Avoid those and you are most of the way there without ever solving the original question.
The same trick is what makes a pre mortem work. Before the launch, assume the project is dead and write the autopsy. Reasons surface that no one would have raised an hour earlier, while the plan still needed defending. The forward question — will this work? — collects the cheerful conformity of people who want to look committed. The inverted question makes the pessimist useful.
It pairs with via negativa but isn’t the same thing. Via negativa is a strategy: improve by removing. Inversion is a single move you make in your head, before deciding what to remove.
!! You can’t compound what you’ve already lost.
It has a ceiling. Inversion finds necessary conditions, not sufficient ones. A marriage without contempt isn’t automatically loving; a portfolio that doesn’t blow up isn’t automatically rich. But you can’t compound what you’ve already lost, and most ruin comes from doing one obvious wrong thing repeatedly, not from failing to find a brilliant right one. Survival comes first. After that the question changes.
The discipline is just remembering to flip. Most problems get attacked head-on out of habit. Pause, ask the inverted version, and a different list appears — usually shorter, often surprising, occasionally the one you needed.