One of the most influential thinkers of the Middle Ages was English Franciscan friar and philosopher William of Ockham. Ockham was the village in the English county of Surrey, where he was born. By misspelling Ockham, his theory became known as Occam’s Razor. It is also called Ockham’s Razor, Law of Economy, and the Law of Parsimony.

William of Ockham didn’t discover the theory, but no one used the principle so persistently. He used it so often that it was associated with him. He wrote in his Summa Logicae in 1323, “It is futile to do with more what can be done with fewer.” In other words, keep it simple; don’t overcomplicate a statement.

The theory went as far back as Aristotle, who phrased it, “We may assume the superiority, other things equal, of the demonstration which derives from fewer postulates or hypotheses.”

Occam’s Razor says that given a set of explanations, the simplest one is the correct one. Isaac Newton restated the principle in his Principia Mathematica in 1687. Newton’s rule stated: “We are to admit no more causes of natural things than such as are both true and sufficient to explain their appearance. Other scientists also adopted the principle. Leibniz phrased it as “identity of observables.”

What is Occam’s Razor Theory?

Occam’s Razor theory is a principle that states that entities shouldn’t be multiplied unnecessarily. In other words, the simplest explanation is preferable to one that is more complex. The simpler the theory or solution, the easier it is to confirm or execute.

It does not make any absolute assertions that the simplest answer is always the correct answer. Occam’s Razor simply suggests that with various solutions, statements, or hypothesis to a question, the one with the least assumptions is often the best.

The logic behind Occam’s theory is that if two competing theories:

  • Explain the same single event
  • With equal persuasion
  • Reach the same conclusion
  • With a satisfactory and plausible explanation, then the less complicated theory is the better option.

The Razor shaves away the unnecessary assumptions that distinguish two competing theories. It cuts through the confusion to exert the best approach based on the knowledge and fact at that time.

Misuse of Occam’s Razor has occurred throughout history. The most common misuse is when simplicity principles are applied to the absolute judge between right and wrong or good and evil. The other misuse is to compare two contrasting theories or hypotheses. Darwin’s natural selection compared to God the Creator is not necessarily a good example of applying Occam’s Razor.

The Razor should be used to simplify testing and make it more reliable, not to test truth or accuracy.

What is An Example of Occam’s Razor?

Example 1: A student failed a test.

Possible explanations are:

  • The student should have studied harder.
  • The teacher purposefully marked the correct answer wrong so that the student may fail in conspiracy with the textbook publisher who printed the wrong study material.

According to Occam’s Razor theory, the first explanation is the more likely one.

Example 2: You sent several text messages to your friend, and they did not reply.

Possible explanations are:

  • Your friend is purposefully ignoring your text message as revenge because you did not answer their phone call a week ago.
  • The battery of your friend’s phone was flat.

According to Ockham’s theory, the second option seems the more likely one.

How is Occam’s Razor Used?

Quantum Mechanics

Occam’s Razor is used in quantum mechanics to justify uncertainty.


Occam’s Razor is used as an abductive heuristic guide, a problem-solving approach, for scientists in developing theoretical models.  Scientists use Occam’s Razor to simplify moving from point A to point B through complex equations.


Ernest Mach called his version of Occam’s Razor the Principle of Economy, which means “Scientist must use the simplest means of arriving at their result and exclude everything not perceived by the senses.”

Physics uses Occam’s Razor to shave away metaphysical concepts. Both Einstein, with his theory of relativity and Lorentz’s argument that the changes take place in the ether, came to the same conclusion. Their theories why, for example, we slow down the closer we get to the speed of light, differed. Einstein’s theory was preferred because it did not mention ether, which, according to scientists, didn’t exist.


In philosophy, Occam’s Razor is the principle that simple explanations are most likely to be correct, and one should avoid implausible or unnecessary assumptions. The Razor shaves off and eliminate unlikely explanations and avoid improbable actions. With two competing hypotheses about the same prediction, one should choose the theory with the fewest assumptions. Occam’s Razor should not be used where hypotheses have different projections.


In 1940, Theodore Woodward taught his medical interns, “When you hear hoofbeats, think of horses, not zebras.” Zebra became the American slang term for a physician giving an exotic medical diagnosis when a more conventional is more likely. Zebra is a variation of Occam’s Razor, where physicians should first consider the more familiar diagnosis before jumping to the conclusion the patient has a rare disease.


Biologist Francis Crick deemed Occam’s Razor a useful tool but dangerous to implement in biology. His skepticism of using the simplest explanation was deduced from the necessity to assume nature was simple, which it is not.


Although likelihood is a synonym for probability, in statistics, there is a clear technical distinction. Information theory, which is close to likelihood, uses Occam’s Razor. Claude E. Shannon founded information theory in 1948. His source coding theorem, a noisy-channel coding theorem, resulted from the learning theory.

Artificial Intelligence

Ray Solomonoff’s theory of inductive inference is the mathematical formalism of Occam’s Razor and the principle of Multiple Explanations. His theory explains observations of the world by the smallest computer program that outputs these observations. The modern application of Solomonoff’s inductive inference is artificial intelligence.

Programming Language

Occam is a computer programming language derived from Occam’s Razor. The primary goal of the language is to keep it simple. The Occam programming language expresses concurrency and is valuable for teaching concepts of parallel algorithms in the message passing paradigm.

Other Uses

  • Richard Swinburne argued simplicity on logical grounds, and those simplicity considerations are part of common sense.
  • Ontological reduction by elimination was applied in history for angelic motors for medieval celestial mechanics, demonic possession as the explanation for mental illness, the four humors of ancient and medieval medicine, and phlogiston theory.
  • Many scholarly papers obtain formal versions of Occam’s Razor from probability theory, applying it in statistical inference and using it for criteria for correcting complexity.

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When applying Occam’s Razor (Ockham’s Razor, Law of Economy, or Law of Parsimony), you could accidentally cut that which was valuable if the Razor is misapplied. Although the simplest explanations may probably be the best, it is not always true. Use common sense when applying Occam’s Razor, and you will not be cut accidentally.

Then again, by keeping it simple, is often the best alternative, especially in a learning environment and where it’s necessary to follow instructions. Students learn easier when a complex topic is explained in simple everyday language.

Occam’s Razor is a valuable tool when applied correctly. People use it daily without consciously realizing it is Occam’s Razor they are applying. Keeping it simple could be more challenging sometimes, because of its simplicity.

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