Occam’s Razor: The Simplicity of Truth

08.03.2019 |

Episode #4 of the course Mental models: How to make better decisions by John Robin


Welcome back!

So far, we’ve learned about two important mental models, and from yesterday’s lesson, we know why we can trust that covering only a few of the best models is enough to get us a high appreciation of the topic.

This is related to the mental model we’ll be covering today. Occam’s Razor is all about why simpler is better and how seeking simplicity is a sure way to make better decisions.


What Is Occam’s Razor and Why Is It True?

William of Ockham was an English Franciscan friar who lived in the early 1300s. He didn’t have the scientific method to work with as a mental model, like later innovators of the Renaissance some 100 years later. Nonetheless, he was revolutionary.

He led a simple life: Despite studying theology at the University of Oxford, he taught his own kind of philosophy based on logic, revolving around the principle he has become famous for.

In Latin (since he wrote and taught in Latin), it’s called lex parsimoniae, which means the law of briefness. This principle, now called Occam’s Razor, can be stated simply: The simplest solution is correct.

Though simple in his time, this got him in trouble with the Church, who considered him a heretic for challenging overly complicated doctrines in light of simpler ideas about the laws of the universe. He fled his home in 1327 and for the last 20 years of his life, led a simple existence of wandering with a group of friars.

Occam’s Razor is named after him, but the mental model itself had already been around. Ptolemy, who lived 1,200 years before William of Ockham, wrote about the importance of choosing the simplest possible hypothesis. Not referencing Ockham, Sir Isaac Newton believed in the power of using the fewest assumptions possible when explaining natural laws.

The reason Occam’s Razor is true relates to the second law of thermodynamics, which states: Whenever possible, energy required is minimal.

Applying this to the behavior of the universe, any collection of particles will tend toward their lowest energy state. In general, this means the universe as a whole tends toward simplicity.

Take, for example, a habit. Every time you train yourself to do something new, it requires energy in the neurons of your brain. If you repeatedly do this action, however, your brain has other neurons that store the memory of what the initial neurons for the new task had to do. Instead of having to put several neurons to work each time, your brain minimizes the energy by making the act automatic—hence, a new habit.


Applying Occam’s Razor

On a day-to-day basis, you don’t have all the facts. You can’t turn your life into a research lab and conduct experiments to get at the exact truth.

That’s why you use Occam’s Razor.

Equipped with this mental model, when assessing your choices and problems, you can operate with the assumption that however complicated a given situation, your goal is to find the simplest solution.

Let’s take an example.

Suppose you have a sore lower back and a splitting headache that hits you every day at 4 p.m. You also take two hours to fall asleep every night and find your mind racing.

These sound like three different problems, and you might go to your doctor to treat them all.

Your doctor will likely ask you simple questions: How is your stress? What do you do before bed?

This is because your doctor understands Occam’s Razor. All these things are likely one problem: You are overworked.

The solution to the problem isn’t getting a better posture chair to fix your back. The solution isn’t analgesics to get rid of headaches. The solution isn’t sleeping medication.

The solution is getting balance in your life so your stress goes down. Then the muscles that seize up in your back from chronic tension relax and so do the muscles in your neck, which are causing the headaches. And guess what? The spike of adrenaline rushing through your body from chronic stress also goes down, slowing your heart rate and promoting sleep so you’re off to dreamland shortly after hitting the sheets.



Seek the simplest solution to any problem in your life, as well as your understanding of how the world works. This is Occam’s Razor and it’s powerful.


Step 1: Make a list of the top five problems in your life.

Step 2: Try to think of one larger problem that explains them (if you can’t think of one, try two).

Step 3: Try to fix that larger problem, and assess how it helps with the five problems.

Tomorrow, we’ll talk about how we can use mental models to predict the future, by way of Bayesian Updating.


Recommended book

A Brief History of Time by Stephen Hawking


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