man muss immer umkehren - Carl Gustav Jacob Jacobi

(loosely translated - Invert, always, invert)

Today, we will look at one of my favourite mental models called - The Inversion principle. Mental models are a set of simple, abstract but useful principles that help us make sense of the world around us.

I came across the Inversion principle on the Farnam Street blog. It is also a favourite of Charlie Munger (Vice Chairman of Berkshire Hathaway and Warren Buffets mate) - "...it is in the nature of things that many hard problems are best solved when they are addressed backward", he pontificates.

In another interview, he recalls how, as an Air Force meteorologist during World War II, instead of asking what would keep pilots safe, he asked what would kill them and focussed all his efforts "on trying to predict snow, ice or fog—and to ignore pretty much everything else.".

I could write a book on all the other cool stuff Charlie Munger has said so I'll stop here.

What is it?

Inversion is based on the maxim - invert, always, invert. It is about considering an inverse (usually a negative) outcome and listing the reasons for these. It forces you to either stop doing certain things or avoid the actions that lead to the negative outcomes. It gives us new possibilities and capabilities that we might not have considered otherwise.

The algorithm for inversion is very simple:

  • Define the problem - what is it that  you're trying to achieve?
  • Invert it - what would guarantee the failure to achieve this outcome?
  • Finally, consider solutions to avoid this failure

This is very abstract and vague, so let's look at a few examples:

  1. Instead of asking how do we increase the adoption of a product or feature? You could instead consider - what are some of things preventing adoption? This would lead to a list like this that you could potentially fix:
  • Slow load time i.e. performance issues
  • Not enough marketing, or marketing on the platform, or to the wrong audience
  • The user guide instructions are not clear ... you get the idea

2.  Following the inversion principle it is better to ask what is preventing me from reading all the unread books on my kindle/bookshelf, instead of asking how can i read more books? Possible reasons and something you could give up:

  • I spend a lot of time on social media
  • I watch too many shows on Netflix or Disney +
  • Spend a lot of time on reddit or browsing hacker news

3. Instead of wondering how do I always choose a winning stock during investing, ask yourself how do you prevent losses in the long term?

  • Am I diversifying enough to prevent long term loss?
  • Am I investing  based on sound principles, or am I speculating?

Hopefully this  gives you a flavour of how powerful inversion is as a mental model. I should add that it is NOT a silver bullet and it won't always give you concrete answers, but it will act as a forcing function to avoid obvious lapses in judgment. I'll leave you with another one of my favourite quotes about Inversion from Charlie.

"It is remarkable how much long-term advantage people like us have gotten by trying to be consistently not stupid, instead of trying to be very intelligent."


Further reading:

Avoiding Stupidity is Easier than Seeking Brilliance
Putting Mental Models to Practice Part 3: Better Trial and Error
Instrumental rationality is the sort of thinking that allows you to achieve your goals. We take a closer look at what decision science says is the ‘best’ way to pursue this purpose.

Thanks for taking the time to read this post, if you found it useful and if you have any comments or more tips, please hit me up on twitter (@anup).