So I just read The Great Mental Models Volume 2: Physics, Chemistry, and Biology by Shane Parrish. A book about improving our thinking using interdisciplinary mental models. It’s the second in a series which started here.

These mental models form a lattice upon which we can frame our thinking. We then are able to evaluate situations with a wider range of ideas and thereby achieve better solutions.

                        book cover

Brought to you by Farnam Street

Using mental models is like practicing shamanism: we summon hidden forces to see more clearly the flow of information and energy. The ultimate goal is to have a broader perspective on problems.

Sometimes that’s all it takes.

The second volume is about mental models inspired from physics, chemistry and biology. I present below those I found the most interesting. Let’s dive in.



Relativity tells us there is no absolute frame of reference. This applies to physics and life.

In physics, someone sitting in a train feels still while someone outside the train sees the same person in movement.

In life, our view of any situation is always different from someone else’s.

Similarly when someone tells a story, it comes from his specific point of view. The story has framing and an agenda which may or may not be aligned with yours.

Relativity invites us to add new points of view to a story because we better see a situation using additional angles. More lenses is good. Inversely, using a single source of truth means we have a single point of failure in our thinking.

For example let’s consider deaths by terrorism relative to other causes in the United States. Using relativity we enlarge the frame and see a different story. A story in which we can ask ourselves whether we should fear terrorism.

                        death statistics

Zooming out shows a different story [Our world in data]

We also improve the information quality when we think about the agenda behind it. Is it well aligned with yours? Would there be a reason for the source to tell a story with hidden parts?

                        deceptive ad

If there's an ad for it you probably don't need it [Art Nectar]

Contrast is what allows us to see. We increase the contrast by having different angles to look from. The more diverse the frames, the better the focus on what’s observed.


Give, and it will be given to you.

– Luke 6:38

We are programmed to be cooperative. We become happier when we share and when we give. However, fear and loss aversion may interfere and prevent us from exploring that aspect of ourselves.

Picture yourself smiling to strangers when you walk. It lightens your day and theirs. It is beneficial for both of you and it works 8 times out of 10. Fear slips in when we think about the 2 times where it fails.

Here, we want to remind ourselves that we gain much more by trying and giving that smile than by not trying. 8 > 2

You can also think about reciprocity in terms of effort: if you want results, you have to work for it. You will never grow anything without giving it time and energy.

Reciprocity is everywhere. Ignoring it could blind us from the real picture.


Reciprocity at sunset in Gaspésie


If there is a glass of water at the edge of your desk, it will fall towards its equilibrium point – the ground – and create disorder.

Thermodynamics tells us that systems tend towards equilibrium and that there is a higher potential for disorder.

When a drop of ink falls into water, the disorder grows and a disordered equilibrium is progressively reached.

                        broken glass

Disordered equilibrium is coming [Gagneet Parmar]

Systems Tend Towards Equilibrium

Imagine a dominant culture living next to a minority culture. Preserving the specificities and the legacy of the minority culture will require energy because it goes against the cultural equilibrium where both cultures blended.

This preservation will last as long as it is fed with energy. Otherwise equilibrium will prevail.

If you fight against equilibriums, do it wisely. It costs energy.

Higher Potential for Disorder

Imagine a regime where the order is tightly maintained. The regime has to watch every citizen because any of them developing contrarian ideas is a threat. It costs a lot and exhausts the regime over time.

Maintaining tight order consumes a large amount of energy. Order is not free.

Friction and Viscosity

When you face resistance you either push harder or put effort in addressing the required effort in the first place.

When you take the second option, you focus on reducing the friction preventing you from moving.

A practical example of using that model is when I decided to migrate from Wordpress.

I disliked the idea of formatting my document on that platform. I wanted a workflow where I can focus on the writing and have very quick and easy formatting, directly in the text using Markdown language.

This is what I now have. I removed some of the viscosity in order to spend less energy when working.

Friction or viscosity are part of any process but we don’t always consider their impact.

What happens if you remove the viscosity during the meetings at work? What happens if we address the old procedures we are used to?


Speed is not velocity.

Speed, defined as the distance covered in a given amount of time, is not velocity, which is defined as the distance covered relative to where we started.

In other words, going fast does not help if you are running in circles: direction matters. You have to think about where you are going and make sure you are actually moving towards that direction.

To increase velocity, you need to understand what limits it.

Shane gives the example of Napoleon who relied a lot on velocity. He made sure to have an unparalleled velocity by boosting the troops self-esteem and by being close to them.

However, Napoleon did not consider how the weather and the supply chain management would impact his precious velocity in his Russian campaign. He lost.

A practical example of using the model is how I self-assessed my progress on the website migration. I decided to wind down on the content production when I noticed I was not progressing on the migration. I decided to go slower but to go where I want.

Constant velocity trumps speed. Make sure you have velocity.


Activation Energy

There are two energy thresholds in any reaction, change or revolution. First, we need energy to break all previous bonds. Second, we need energy to create new bonds.

We have to consider both energy levels when thinking about change. If we don’t, we risk facing discouragement or failure.

Let’s consider a revolution. If the energy is mostly focused on part one, breaking the bonds and removing the old system, what energy is left to rebuild the system, to form new bonds?

If there is not enough energy, the new system will likely default to what existed previously.

Change occurs by breaking old bonds and creating new ones. If you want change, invest more energy than you think.

Be relentless until the new bonds have formed.


Catalysts are accelerating change that occur anyway. Think the Internet or the printing press.

Find the catalysts in your life. A catalyst could be a mentor, a circle of friends, your family, someone inspiring. Some people will push you up and help you be a better version of yourself.

For example, I recently discovered Akira the Don, an artist producing content that inspires me to push the limits. Be it in training or in learning.


Natural Selection

Natural selection teaches us that as the environment changes, the pressure on the organisms within that environment changes. The organisms either adapt or die. They must fit the environment and withstand its variability.

Natural selection applies to species as well as to ideas.

Let’s leverage that model by considering how our ideas evolve which by extension also defines how we adapt.

How do ideas adapt to a shifting environment?

To adapt they must be in contact with the environment. The idea much like the organism has to feel the environmental pressure. Feedback loops will increase an idea exposure to challenging scenarios.

In other words, an idea that is not challenged is a weakening idea.

You tap into the biological engine of natural selection by honestly challenging your ideas and models. Simple and yet complex.


Ecosystems exist as entities made of different components. Ecosystems interact with each other because they are never truly closed. Their components are in constant fluctuation.

All ecosystems are connected and all systems are connected.

This implies we need to deploy extended thinking to go beyond the component we see because it’s never standing on its own. Observing how systems are built and interact with each other helps us move beyond linear cause and effect.

Imagine your team is under delivering. You can look for answers among the team members but maybe the answer lies elsewhere. It could be related to the environment, its ecosystem.

Is there too much viscosity? Could we be missing reciprocity? What if we follow natural selection and start challenging our assumptions?

Our mental models are connected too.

Thinking in silos produce a simplified version of reality. Mind the gap between reality and your simplification.

Closed systems produce fewer and fewer innovations because closed systems, by definition, are based on certain increasingly unchallengeable fundamental principles”

– Gary Hart


Within an ecosystem, some organisms dwell in large niches. They are generalists. Some others dwell in small niches. They are specialists.

Generalists face more competition. Their daily stress is higher but they are better equipped to face environmental changes.

Specialists have fewer competitors. They are not daily stressed but face high stress should the environment change.

                        generalist versus specialist

The generalist versus the specialist [Cloudtail & Wikipedia]

Both types are good, but it is important to be aware of the trade-offs. What type are you?


Cooperation teaches us that it is better to work together than alone because it frees up resources. Cooperation works. Humanity is built upon thousands of layers of cooperation: languages, religions, nation States, etc.

We often think in terms of competition but sometimes we acquire a real edge by discovering how to collaborate with our competitors.

Hierarchical Organization

Hierarchies exist everywhere and it’s partially due to instinct.

We all look for leaders, even if we are looking at ourselves.

– Shane Parrish

They present advantages. They offer a clear flow of information. They allow a clear distribution of responsibilities. They tend to be stable. There is a reason why armies, organizations facing very high stake situations, are hierarchical.

They also present weaknesses. They put a lot of pressure at the bottom and the top. They are unfair: not every ladder is fairly rewarded for its contribution. Good ideas coming from the bottom may be refuted simply based on rank.

We can’t refute or accept hierarchy blindly. Hierarchies can serve us if used properly.


Incentives are drivers behind our behaviors. Some are obvious but often they are hidden. Those are the ones we should to be wary of.

Out of sight incentives lead us to odd behaviors where we pursue the hidden incentive against our desire.

Think of doctors prescribing bad drugs thinking they are helping because they were subtly lobbied a few months before. Unknowingly to them, the misalignment of incentives leads them to disregard conflicting evidence.

Being aware of our own incentives is important to understand why we are on a specific track. Know your incentives. Are they yours? Do they lead you in the right direction?

Energy Minimization

Energy minimization is seen a lot in biology. It helps but hurts sometimes.

Energy minimization is why we use heuristics (quick mental shortcuts). Effective, but sometimes flawed. See my previous article on those shortcuts and cognitive fallacies here.

Jumping to conclusions is efficient if the conclusions are likely to be correct and the costs of an occasional mistake acceptable, and if the jump saves much time and effort. Jumping to conclusions is risky when the situation is unfamiliar, the stakes are high, and there is no time to collect more information.

– Daniel Kahneman

End Note

I hope you will enjoy playing around with your own mind and ideas. The whole point is to have fun getting smarter, to enjoy destroying your old models and expand your thinking.

Thank you for reading.

Thanks Flavie, Alex and @Zach_of_Earth for their precious feedback.