Occam's Razor as a Scientific Principle

Margaret Hagen, Artem Cheprasov
  • Author
    Margaret Hagen

    Maggie has her BS in Biology from Murray State University and her MS in Cell and Molecular Biology from Saint Louis University. She has many years of tutoring, editing, and writing experience and teaches college-level biology courses.

  • Instructor
    Artem Cheprasov

    Artem has a doctor of veterinary medicine degree.

Discover the philosophical principle of Occam's razor. Study examples from history, the potential pitfalls of Occam's razor and how to use this principle. Updated: 09/24/2021

Table of Contents


What Is Occam's Razor?

A woman is sitting on her couch on a rainy evening watching a scary movie. She notices through the corner of her eye a flash of light outside her window. Two theories come to mind for what might have caused this:

  1. The rain has turned into a thunderstorm, and it was lightning.
  2. A UFO just abducted someone outside her house.

While the movie she is watching may lead her to suspect alien intervention, it is far more likely that the light was due to a storm. The logical tool used to determine the cause of this light will be discussed in this lesson.

Occam's Razor Definition: The Simplest Solution

Occam's Razor (also sometimes spelled Ockham's Razor) is a principle stated initially in Latin: Pluralitas non est ponenda sine necessitate this translates to 'Plurality should not be posited without necessity.'

  • In other words, the simpler one is better when two competing theories make the same predictions. Complexity does not always make the theory better; it makes it less likely.

This principle is sometimes used interchangeably with the law of parsimony, which states that 'The best explanation is the one that requires you to make the fewest possible assumptions.' These both generally state that the simplest explanation is usually the best.

  • Some say that the law of parsimony broadens the scope a little bit, as it is not confined to theories that would lead to the same result but can be used to weigh the probability of entirely different predictions

Occam's razor is a principle used to determine which of two theories is more plausible

razor illustration with William of Ockam engraved

Who Came Up with the Occam's Razor Theory?

The Occam's Razor principle is credited to a Franciscan philosopher named William of Ockham in the mid 14th century.

  • He was not the first to have the thought, as other philosophers had discussed the idea before going back as far as Aristotle and Galileo.
  • Ockham condensed the concept into a simple statement and used it repeatedly and sharply, so it became known as "Ockham's Razor."

Occam's Razor Meaning

While it is clear that the "Occam's" portion refers to the principle's architect (misspellings led to the modern spelling "Occam" instead of William's spelling "Ockham"), there is more confusion surrounding the other half of the name.

  • Some people suggest that the "Razor" part of the name was due to the sharpness with which Ockham used the principle.
  • Most believe that it refers to the cutting away of superfluous assumptions to find the simpler truth.

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Occam's Razor Examples

This principle can be used to quickly find answers in many areas of life, both scientific and ordinary. Below are a few examples of scenarios where people had to choose between two alternate explanations. In each case, Occam's Razor could be used to determine which theory is most plausible.

Example 1:

A man's phone rings, and he does not recognize the phone number. He wonders if:

  • It is a telemarketer or some other type of spam call. OR
  • He has found himself in an international conspiracy, and spies are trying to use the call to track his location so that they can kidnap him.

Example 2:

A person wakes up with a headache after a night of heavy drinking. They decide to search the internet to diagnose the problem. They determine that it is one of two things:

  • They have a disease that affects the blood vessels of their brain. OR
  • They are dehydrated.

Example 3:

When early scientists were trying to determine how the planets of the solar system move, they had trouble explaining the observations of retrograde motion, where some planets appeared to move backward, there were two main theories:

  • Ptolemy suggested geocentrism, or the idea that the planets and sun revolve around the earth, but added an addendum that the planets also move in their own individual circles on the rotations around the earth. Except the sun and moon do not have secondary circles. OR
  • Kepler proposed heliocentrism or the concept that the planets revolve around the sun.

a) Ptolemy's Geocentric Proposal b) Kepler's Heliocentric Theory

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Frequently Asked Questions

Is Occams razor valid?

Occam's razor is valid in some cases, but in others the correct explanation is a more complex option. This is why Occam's razor should be used as a guiding principle rather than an absolute rule.

What is Occam's razor in layman's terms?

In simple terms, Occam's razor states that when choosing between two explanations for an observation, the simpler explanation is more likely to be correct.

How is Occam's razor used?

Occam's razor is used to determine which explanation for a phenomenon is more likely to be true. It states that the observation that is simpler is usually better.

What is meant by Occam's razor and when would you use it?

Occam's razor is a tool used for determining what solution or explanation is most likely to be correct. It can be used any time that there is more than one possible explanation for something, but it should be combined with empirical testing or observations before a conclusion is made.

What is an example of Occam's razor?

If someone has a headache, it is more likely that they are simply dehydrated than it is that they have a brain disease.

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