Occam’s Razor Explained

william of ockham stained glass

In this post I’m going to explain Occam’s Razor, give you a little background on where it comes from, and provide some examples to help you get a better grasp of this mental model.

Occam’s Razor is a philosophical razor that states, entities should not be multiplied beyond necessity. It is often paraphrased today as, the simplest explanation is usually the best one.

Occam’s Razor is also known as the Law of Parsimony. Parsimony is just a ten-cent word that means to be extremely thrifty or careful with resources. Coocam’s Razor is parsimonious in that it says we should look for the simplest explanations when in search of the truth.

Explaining Occam’s Razor

Occam’s Razor works as a rule of thumb that can be used when you’re faced with a number of competing explanations for a given situation or phenomenon.

It says that the simplest explanation is usually the best one, or conversely, that unnecessarily complex and convoluted explanations are unlikely to be correct.

It advocates for simplicity, or parsimony, and helps you choose the most likely explanation by eliminating those that are needlessly complex.

But why is it called a “razor”?

What is a philosophical razor?

In philosophy, a razor is a principal or rule of thumb used to shave away unnecessary ideas or theories.

Other notable philosophical razors include Hanlon’s Razor and Hume’s Guillotine. Each one of these applies a principal or rule of thumb to eliminate unlikely options, arguments, or ideas.

And that’s exactly how Occam’s Razor works. It’s a rule of thumb used to cut away less likely explanations.

I’ll give you an example of Occam’s Razor in action in just a minute. But first, let’s talk about where this philosophical razor gets its name.

About William of Ockham

Occam’s Razor is named after William of Ockham, a 14th century Franciscan Friar, theologian, and scholastic philosopher. He was born in the town of Ockham, located in Surrey, England and attended Oxford.

William spent six years at Oxford and did enough work to be granted his masters, but for reasons we don’t know, he never received that honor.

Regardless, William went on to teach and write and is a major figure in medieval thought, having produced important works on logic, physics, and theology.

In fact, he was often at the center of the significant intellectual and political controversies of his day, and even went as far as to publicly call Pope John 22 a heretic.

Unsurprisingly, in hindsight at least, William of Ockham was eventually excommunicated from the Roman Catholic Church.

What’s interesting about Occam’s Razor is that William of Ockham didn’t really invent it. Aristotle, Ptolemy, Aquinas, and Duns Scotus all promoted the law of parsimony, which is what Occam’s Razor is, well before William of Ockham.

An example of Occam’s Razor in use

Okay! So we’ve covered how Occam’s Razor works, explained philosophical razors, and talked about William of Ockham’s background. Now it’s time for an example.

Let’s say you live in an apartment building in NYC that’s next to a railway line. As you’re watching television, a loud rumble overwhelms you. Is that loud noise a train going by or is it a herd of African water buffalo stampeding on the street below?

The simplest explanation is that it’s a train.

A caution for using Occam’s Razor

I must caution you that it’s possible to oversimplify and end up with the wrong answer.

For example, someone might go to the doctor with flu-like symptoms: headache, sore joints, and a fever. The doctor, using Occam’s Razor, might conclude they’ve got the flu, since that’s the simplest explanation. But, it’s possible that further tests might reveal a more serious problem, like Lime Disease.

The two things to keep in mind if you want to avoid misapplying Occam’s Razor is first, remember it’s just a rule of thumb, and not a law. Second, always get as much information as you can before eliminating possible options. Keeping these things in mind will help you avoid jumping to the wrong conclusion.


So, there you have it! Occam’s Razor, named after William of Ockham, is a philosophical razor that states the simplest explanation is often the best one. It’s a rule of thumb that’s best applied to eliminate unlikely explanations after you’ve reasonably collected as much data as possible.