• Before making a single edit, Tropedia EXPECTS our site policy and manual of style to be followed. Failure to do so may result in deletion of contributions and blocks of users who refuse to learn to do so. Our policies can be reviewed here.
  • All images MUST now have proper attribution, those who neglect to assign at least the "fair use" licensing to an image may have it deleted. All new pages should use the preloadable templates feature on the edit page to add the appropriate basic page markup. Pages that don't do this will be subject to deletion, with or without explanation.
  • All new trope pages will be made with the "Trope Workshop" found on the "Troper Tools" menu and worked on until they have at least three examples. The Trope workshop specific templates can then be removed and it will be regarded as a regular trope page after being moved to the Main namespace. THIS SHOULD BE WORKING NOW, REPORT ANY ISSUES TO Janna2000, SelfCloak or RRabbit42. DON'T MAKE PAGES MANUALLY UNLESS A TEMPLATE IS BROKEN, AND REPORT IT THAT IS THE CASE. PAGES WILL BE DELETED OTHERWISE IF THEY ARE MISSING BASIC MARKUP.


WikEd fancyquotes.pngQuotesBug-silk.pngHeadscratchersIcons-mini-icon extension.gifPlaying WithUseful NotesMagnifier.pngAnalysisPhoto link.pngImage LinksHaiku-wide-icon.pngHaikuLaconic
File:SweeneyTodd OccamsRazor 9415.jpg

William of Ockham, preparing to murder yet another elaborate theory.

"You know, [this] has taught me a valuable lesson; the best solution to a problem is usually the easiest one. And I'll be honest — killing you is hard."
GLaDOS, Portal 2

Also called:

  • Law of parsimony
  • Law of economy
  • Law of succinctness
  • The Lex Parsimoniae

Occam's Razor is a logical principle first described in the 14th century by William of Ockham, an English Franciscan friar and philosopher. It is often used to evaluate the usefulness of a theory. Its main tenet is that "Entities must not be multiplied beyond necessity." It can be summed up with the phrase "When you hear hoofbeats, think horses, not zebras."

Most theories have a foundation of underlying premises (the aforementioned "entities"), all of which need to be true for the theory itself to be true. Occam's Razor suggests believing the theory with the fewest underlying premises (the aforementioned "not multiplied beyond necessity").

Example: There have been theories that Ancient Astronauts built the Egyptian Pyramids instead of humans. For this to be true, we'd need the following givens:

  1. aliens exist[1],
  2. they have some form of interstellar travel[2],
  3. they know how to find us[3], and
  4. once they got here, they'd waste time building huge stone things in a desert instead of, you know, actually showing themselves.

The more normal theory only requires that

  1. humans exist[4], and
  2. said humans would waste time building huge stone things in a desert[5].

You can probably guess which theory Occam would agree with, and why.

It's the bane of Conspiracy Theorists everywhere for the same reason: take a look at the Apollo moon landings, which a good percentage, in the single figures, believe was hoaxed. Often people will find "evidence" that the landings could never have taken place, but it rests on the arguments that the US government

  1. were willing to throw billions away for smoke-and-mirrors attempts,
  2. were smart enough to fool 90% of the population (which some would contest),
  3. were simultaneously stupid enough not to cover their tracks,
  4. were able to pay off and swear to silence thousands of people working at NASA and other companies for forty years when they couldn't even pull off a simple burglary, and
  5. were actively collaborating with the Soviets during a period of history where relations were historically edgy and were given consent by Moscow to win this symbolic victory.

After that, you'd think that the simplest explanation was to, you know, actually send people there (That Mitchell and Webb Look has a brilliant series of sketches on this idea, including the moon landing).

The Razor is commonly misinterpreted as saying, "The simplest theory is the best." This is not correct in Real Life unless it is the simpler of two theories which make predictions with identical degrees of accuracy. All other aspects of the theory have to be equal before simplicity is taken into account. It also requires that all the data is accounted for. Newtonian physics are simpler then modern theories and were sufficient to take man to the Moon, but (with all due respect to the man) Sir Isaac simply could not explain all the data eventually collected--especially since a lot of the offending material had not been collected when Principia Mathematica was published. This required some other smart man--fellow named Albert Einstein--to formulate more complex theories, particularly the outrageous stew we call "Relativity" which functions along completely different rules. Now, Occam's Razor would suggest that there must be some Grand Unified Theory that explains why physics work one way on an atomic level and completely differently on a larger-than-atomic level. Much of the last century of scientific research (including Einstein's) has centered around trying to come up with one. They haven't succeeded. So far, Occam's Razor is wrong, and the universe simply functions according to completely different sets of rules depending on an object's physical size, for no good reason whatsoever. Nobody likes this, but in the end, nothing says that an explanation must be simple.

Another very common mistake is to summon up the Razor in a debate over a point that is entirely moot in order to add weight to a particular argument. This usage is entirely fallacious as the Razor does nothing more than recommend the hypothesis that makes the fewest new assumptions. It is not a magical tool that points to the right answer. In a lab it will be used hundreds or thousands of times, with each and every one of the chosen hypothesis being rigorously tested, before a correct answer is found. In a debate the Razor will be used once and will, invariably, choose the user's answer as the 'right' one. Funny, that.

And always remember that Occam's Razor is a guideline, not a rule. Be careful of facts that are subjective in nature or may not be fully established.

  1. This is probably true; the Milky Way is a big place
  2. This is certainly not impossible, but it'd be difficult to falsify; our modern science today hasn't the faintest clue how to get to other stars, and the farthest-flung manmade object--Voyager 1--is maybe two light-weeks from Earth
  3. Absolutely false; Sci-Fi Writers Have No Sense of Scale
  4. This is factually true, solipsism notwithstanding
  5. Which certainly seems untrue, but humans have wasted time building huge stone things elsewhere, so why not a desert?