Occam's razor

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the maxim that assumptions introduced to explain a thing must not be multiplied beyond necessity.
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Origin of Occam's razor

First recorded in 1900–05; after William of Occam
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2022


What does Occam’s razor mean?

Occam’s razor is a philosophical principle that states the simplest explanation is usually the best one.

How do you pronounce Occam’s razor?

[ okuhmz rey-zer ]

Where did Occam’s razor come from?

Occam’s razor is grounded in the idea of parsimony—being thrifty with your resources. Just as we all strive to pinch our pennies, Occam’s razor teaches us that we should hold off on our hypotheticals.

The phrase Occam’s razor is recorded in 1852 by the Scottish metaphysician Sir William Hamilton. Hamilton credited William of Ockham, a 14th-century English monk and philosopher, with formulating his namesake, Occam’s razor: “More things should not be used than are necessary.” In other words, when trying to make sense of some phenomenon (especially between two competing alternatives), it’s best to avoid the more elaborate explanation—shave it off, like a razor.

If it looks like a duck, swims like a duck, and quacks like a duck, says Occam’s razor, it’s probably a duck. Not a goose disguised as a duck that infiltrated the flock. Sure, that hypothetical exists. We can’t 100% rule out that it didn’t happen. But it’s most likely a duck.

Many folks first encounter Occam’s razor in school when learning about the scientific method and learning about how to create testable and falsifiable hypotheses. Occam’s razor compels us to form the simplest hypothesis that is consistent with the data available.

The principle is also commonly applied in modes of reasoning in philosophy, math, and religion—and, of course, The Simpsons in 1994, when Lisa cites Occam’s razor to dismiss some outlandish hypotheticals.

Some critics of Occam’s razor, however, state that the principle is an oversimplification of the complexities of real life and often rules out creative thinking.

How to use the phrase Occam’s razor

Outside of discussions in science and logic, some people casually cite Occam’s razor as a handy rule of thumb to make sense of life and all its messes. Others apply it more sharply to politics, especially to bust conspiratorial thinking.


Thanks to its name, Occam’s razor invites plenty of puns too.

More examples of Occam’s razor:

“With Occam’s Razor inspiring our designs, we can achieve views that are elegant in their simplicity and are all about user speed and efficiency. Something Alexa and her virtual assistance sisters can well appreciate and strive to deliver.”
—Deb Miller, CMSWire, June 2018


This content is not meant to be a formal definition of this term. Rather, it is an informal summary that seeks to provide supplemental information and context important to know or keep in mind about the term’s history, meaning, and usage.

How to use Occam's razor in a sentence

British Dictionary definitions for Occam's razor

Occam's razor

a variant spelling of Ockham's razor
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Scientific definitions for Occam's razor

Occam's razor
Ockham's razor (ŏkəmz)

A rule in science and philosophy stating that entities should not be multiplied needlessly. This rule is interpreted to mean that the simplest of two or more competing theories is preferable and that an explanation for unknown phenomena should first be attempted in terms of what is already known. Occam's razor is named after the deviser of the rule, English philosopher and theologian William of Ockham (1285?-1349?).
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.