William of Occam was a 14th-century English friar, philosopher, and theologian. He’s considered one of the prominent figures of medieval thought and was involved in many major intellectual and political controversies during his time.
William is most commonly known for the methodological principle called Occam’s razor. He did not coin the term himself, but his way of reasoning inspired other thinkers to develop it.
Occam’s razor is basically a rule of thumb for problem-solving which states that: “Among competing hypotheses, the one with the fewest assumptions should be selected.” Another way of putting is that the simplest solution is probably correct.
Using Occam’s razor, you “cut away” what’s excessively complex so you can focus on what works. This approach is used in a wide range of situations to improve judgment and make better decisions. To understand how, let’s have a look at a few examples.
Many great scientists have used Occam’s razor in their work. Albert Einstein is one of them. His version of the same principle was: “Everything should be made as simple as possible, but not simpler.” This preference for simplicity shows in his famous equation E=MC2. Rather than settling for a complex, lengthy equation, Einstein boiled it down to its bare minimum.
Medical interns are often instructed: “When you hear hoofbeats, think of horses, not zebras.” The underlying idea is to always consider obvious explanations for symptoms before turning to more unlikely diagnoses. This version of Occam’s razor helps reduce the risk of over-treating patients or causing dangerous interactions between different treatments.
By using a combination of statistical knowledge and experience, Occam’s razor can be used in solving crimes. For example, women are statistically more likely to be killed by a male partner than anyone else. So, if a woman is found in her locked home murdered, the first person to look for is any male partners. By focusing on the most likely perpetrators first, the police can solve crime more efficiently.
As a mental model, Occam’s razor works best for making initial conclusions with limited information. To use it, you compare the complexity of different options and favor the simplest one. Imagine, for example, that you come home one day and find that your living room window is open. This surprises you, as you’re usually very diligent in closing it. There are two possible explanations for this:
The first explanation only requires a little mindlessness on your part. The second explanation, however, means someone had to open your window from the outside, disarm your alarm, avoid detection by neighbors, clean up behind them, and leave just as quietly as they came. Therefore, in the absence of any evidence to the contrary, the first explanation is the simplest and the most likely to be correct.
Occam’s razor obviously isn’t perfect. There are exceptions to every rule, and you should never follow them blindly. But, in general, favoring the simple over the complex will improve your judgment and help you solve problems faster and better.