Mental Models for Product Managers: The Inversion Principle

For the last few months, I’ve been applying a mental model to my work as Product Manager which has proven particularly useful: The Inversion Principle.

The Inversion Principle is the perfect example to introduce you to the concept of mental models, and how they can help us in our daily lives, so I’ve decided to write this post to organize my ideas and share them with you.

What is a mental model?

A mental model is quite simply a way of thinking that helps us to process the world around us in a more effective way. In more technical terms we could call them hacks or routines that our brain uses to simplify the outside world.

Nowadays, almost everything we read on the Internet about mental models we owe to Charlie Munger, the legendary investor and Warren Buffet’s right-hand man, who in 1994 gave a speech in the USC Business School (video/ transcription) in which he described how he used them:

What is elementary, worldly wisdom? Well, the first rule is that you can’t really know anything if you just remember isolated facts and try and bang ’em back. If the facts don’t hang together on a latticework of theory, you don’t have them in a usable form. You’ve got to have models in your head. And you’ve got to array your experience — both vicarious and direct — on this latticework of models. You may have noticed students who just try to remember and pound back what is remembered. Well, they fail in school and in life. You’ve got to hang experience on a latticework of models in your head.

Charlie Munger. Rockstar of mental models. Photo CNBC.

What are the models? Well, the first rule is that you’ve got to have multiple models — because if you just have one or two that you’re using, the nature of human psychology is such that you’ll torture reality so that it fits your models, or at least you’ll think it does. You become the equivalent of a chiropractor who, of course, is the great boob in medicine. It’s like the old saying, “To the man with only a hammer, every problem looks like a nail.” And of course, that’s the way the chiropractor goes about practicing medicine. But that’s a perfectly disastrous way to think and a perfectly disastrous way to operate in the world. So you’ve got to have multiple models. And the models have to come from multiple disciplines — because all the wisdom of the world is not to be found in one little academic department. That’s why poetry professors, by and large, are so unwise in a worldly sense. They don’t have enough models in their heads. So you’ve got to have models across a fair array of disciplines.

As we can see, Munger uses mental models to process all the information he absorbs, both from what he reads and his own experiences. These models then form a catalog, from which we can extract the one we need according to the situation, and apply it in the real world.

The Inversion Principle

One of the mental models that Munger has discussed on several occasions is the Inversion Principle, which is based on a maxim by the German mathematician Carl Gustav Jacobi: “Invert, always invert” .

Carl Gustav Jacobi. Photo Wikipedia.

Jacobi made important contributions to the mathematics of his day, and one of the ways he dealt with the most difficult conundrums was to invert them.

Munger explains the concept using India as an example:

“Think forwards and backwards — invert, always invert.” “Many hard problems are best solved when they are addressed backward.” “The way complex adaptive systems work and the way mental constructs work is that problems frequently get easier, I’d even say usually are easier to solve, if you turn them around in reverse. In other words, if you want to help India, the question you should ask is not “how can I help India,” it’s “what is doing the worst damage in India? What will automatically do the worst damage and how do I avoid it?”

Naturally, we have to confront problems head-on, starting from the beginning. However, Munger highlights the importance of first approaching the issue from the opposite angle, to ensure that we have considered everything that would ultimately prevent us from achieving our objective.

Applying the Inversion Principle to developing better products

The process of using the Inversion Principle is very simple:

  1. Define the problem: What is the problem you are trying to solve?
  2. Invert it. What would you have to do to guarantee the failure of your objective?
  3. Consider the solutions. What would you have to do to avoid the failure that you identified in the previous step?

Let’s apply this logic to a real-life example. Imagine we are Product Managers of an e-commerce, and we want to increase the conversion rate.

Instead of thinking about what we could do to increase it, let’s invert the question. What would guarantee that our conversion rate does not increase?

Here are a few examples that come to mind:

  • Not giving visitors the confidence to become customers
  • Complicating the buying process by making the customer create an account
  • Having an unreliable or unresponsive application
  • Not offering all possible payment methods
  • Not offering a compatible version for all possible devices
  • Including unnecessary information on the product pages

Once we have a list of things that will guarantee our failure, we can start to look for solutions. Let’s take a closer look at the first three points on the list:

Not giving visitors the confidence to become customers

We know unequivocally that one way of ensuring our conversion rate does not increase is if the clients do not trust our product. What could we do to build trust?

  • Make sure the app is well designed and looks professional
  • Include high-quality images of the products
  • Highlight our contact details, including phone number, so the customer knows that if they have a problem of any kind, a member of our team will be available to offer support
  • Display accessible, clear information about the buying process: orders, refunds, delivery, etc.
  • Explain who we are and why the client should trust us

Complicating the buying process by making the customer register an account

Introducing a registration process can make a lot of customers abandon their shopping cart. What could we do to minimize the chances of this happening?

  • Firstly, consider this: is it really necessary for the user to have to create an account to buy a product? Could we avoid it altogether?
  • If not, how can we simplify the process? For example, does the user really have to think of a username and a password? Their username could be their email address, and instead of choosing a password, we could email them an activation link to validate their account.

Having an unreliable or unresponsive website / app

Few things are more frustrating than clicking ‘proceed to checkout’, only to find a slow server or an error message prevents us from completing the purchase. To resolve this issue, we could implement performance constraints on our app which the technical team would be responsible for ensuring. For example:

  • The total size of each request between our app and the customers' device cannot exceed 1MB
  • The system must have a 99,99% availability rate
  • The system must be able to withstand a load of 1,000 users per second for intervals of 15 minutes
  • Less than 0,5% rate of errors in our error-tracking service

Simple, right? The great thing about the Inversion Principle is that it forces us to focus on the things that are most critical to our goal, and, as Munger himself says, long-term it’s much more effective to consistently avoid errors than to always try to make progress.

“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.” Charlie Munger.

Other examples of the Inversion Principle

Let’s look at other ways we can apply the Inversion Principle outside the field of Product Management.

Applying the Inversion Principle to achieving personal goals

A few months ago, I had a small crisis at the sheer volume of unread books that were accumulating around my house, so I began to look for a solution using the Inversion Principle.

What could I do to ensure that I could never read all the unread books in my house?

  • Waste time on social media
  • Read too much online news
  • Watch too much Netflix and other streaming services

Once I worked out how to guarantee failure, I took the following measures:

  • I uninstalled all social media apps
  • I blocked the URLs for the main digital news outlets on my devices
  • I watched a maximum of one TV episode per day

The results were almost immediate, and in due course, my pile of unread books started to go down.

Applying the Inversion Principle to your relationship

Can the Inversion Principle be applied to relationships? Let’s test it out. Firstly, what would guarantee the failure of a relationship?

  • Not communicating regularly
  • Not being empathetic, or putting yourself in the other person’s shoes
  • Not being a trustworthy person

Applying the Inversion Principle to being a good leader

This is especially useful for people who are in charge of a team. Firstly, what would make a bad leader?

  • Not having a clear strategy and constantly changing your mind
  • Micromanaging your team and telling them ‘how’ instead of explaining ‘why’
  • Not doing regular, individual meetings with the members of your team to help them with their professional development
  • Not being transparent, and withholding information you receive from other parts of the company

Applying the Inversion Principle to improving your life

Let’s get philosophical for a moment. What will guarantee you have a miserable life in the future?

  • Not making the most of every moment with your family
  • Not taking care of your mind and body
  • Spending beyond your means


As you can see, there are endless ways in which we can apply the Inversion Principle, because, at the end of the day, it’s nothing more than a tool which forces us to consider problems from a different perspective.

I am particularly drawn to hacks which force me outside of my comfort zone, because, in my own experience, it’s not enough to always stick to what we know without considering other ways of doing things.

For those who didn’t previously know about mental models, I hope you found this post interesting! I also hope to continue writing about this, and other subjects, in the future. It’s been a pleasure to share this with you, and I leave you with a few links so you have some great reading material for the coming weeks. Enjoy!

If you liked this article, don’t forget to like 👏 and share it so others can enjoy it too. Thanks in advance!

Other mental models

There are hundreds of mental models which we can apply in our daily life. Here is a list of the most useful links I have found:


Articles about the Inversion Principle which helped me write this post:



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