Bobamnertiopsis via Wikimedia Commons // Public Domain 
Bobamnertiopsis via Wikimedia Commons // Public Domain 

10 Rules, Laws, and Theorems You Should Know

Bobamnertiopsis via Wikimedia Commons // Public Domain 
Bobamnertiopsis via Wikimedia Commons // Public Domain 

You may be familiar with Murphy’s Law and the Peter Principle, but the world is full of wisdom distilled into simple rules for understanding life, human nature, and the world around us.


The Pizza Theorem [PDF] states that you can pick an arbitrary point on a pizza, arrange an even number of slices to meet at that point, and you’ll find that the sum of the areas of alternate slices are equal. This is fine if you're sharing a pizza with only one other person. But the easier Pizza Theorem by Eric W. Weisstein is for calculating the volume of a pizza using the thickness (a) and radius (z). The formula is: pi z z a.


Occam's Razor proposes that when more than one explanation is available to solve a problem and/or predict outcomes, the simplest one is probably your best bet. The opposite rule is Arkham's Razor, which holds true in fiction, particularly comedy: “When given multiple explanations for an event, the oddest one is most likely to be true.” After all, the essence of comedy is the unexpected.


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Trying to suppress something, only to have it blow up in the news as a result, is known as the Streisand Effect. It takes its name from singer Barbra Streisand, who, in 2003, sued the California Coastal Records Project over pictures an aerial photographer took of her house, claiming the photos violated her privacy. Few knew about the images before the lawsuit (in fact, they'd only been viewed six times—and two of those were her lawyers); now everyone does. She lost the lawsuit.


Betteridge's Law of Headlines states that "Any headline which ends in a question mark can be answered by the word no." If the answer is yes, then the headline would simply make that declaration. A question in a headline implies that either 1.) The writer doesn't have enough facts to be sure of the answer, 2.) The question makes the available information more sensational, or 3.) The writer is honestly just asking for the reader’s input.

Ian Betteridge responded to such a headline in 2009, leading to the law in his name. In academia, the same principle is enshrined in Hinchcliffe’s Rule.


When two laws contradict each other, we have a paradox. The Buttered Cat Paradox states that since a slice of buttered toast, when dropped, always lands butter side down, and cats always land on their feet, then if you attach buttered toast to the back of a cat and drop it, neither the cat nor the toast will land on the ground. The working theory is that this phenomenon can be harnessed for its potential energy, but no one has yet demonstrated this.


Geoff Cohen observed that “The likelihood that any unmoderated group will eventually get into a flame-war about whether or not to have a moderator approaches one as time increases.” This became known as Cohen’s Law. Shirky expounds on the internet group dynamics at work here.


If you're tempted to leave a comment to correct someone’s grammar or spelling, beware of Skitt’s Law, which states, “Any post correcting an error in another post will contain at least one error itself.” While such an occurrence appears to be karma, a different wording shows a more generous view of the poster’s intentions: “The likelihood of an error in a post is directly proportional to the embarrassment it will cause the poster.” Skitt wasn't the first to propose this law. It appears under other names as far back as 1990, when Bell’s First Law of Usenet was proposed. The easiest-remembered name for this law is Muphry’s Law, which is a typo of Murphy’s Law, first proposed in 1992.


Cunningham's Law is related to Skitt’s law in that it is born from the urge to correct others’ mistakes. According to the law, “The best way to get the right answer on the Internet is not to ask a question, but rather to post the wrong answer." Internet users can easily ignore a request for help, but have a hard time resisting the urge to appear smarter than the original poster.


Randall Munroe at xkcd // CC BY-NC 2.5

The worst thing you can say about someone is that they remind you of Adolf Hitler, right? It's an easy insult to hurl, so it shouldn't come as a surprise that the comparison is used even when it isn't called for. Mike Godwin noticed this trend on the internet and coined Godwin’s Law in 1990. The law states, “As an online discussion grows longer, the probability of a comparison involving Nazis or Hitler approaches 1." The takeaway is that the person who mentions Hitler has no further information to add at that point, but wishes to emphasize his hatred for the subject of the discussion.


Although most of Clay Shirky’s writing revolves around the internet and new media, the Shirky Principle covers the world at large as well. It reads, “Institutions will try to preserve the problem to which they are the solution.” For example, an organization may want to make their procedures simpler, so they form a committee, or even a new management level, to simplify things. However, adding an extra layer of bureaucracy only makes what you’re doing more complicated.

Wolfgang via Flickr // CC BY-ND 2.0
8 Legendary Monsters of Christmas
Wolfgang via Flickr // CC BY-ND 2.0
Wolfgang via Flickr // CC BY-ND 2.0

The customs of the holiday season, which include St. Nicholas Day, New Years Day, and Epiphany, as well as Christmas, often incorporate earlier pagan traditions that have been appropriated and adapted for contemporary use. Customs that encourage little children to be good so as to deserve their Christmas gifts often come with a dark side: the punishment you'll receive from a monster or evil being of some sort if you aren't good! These nefarious characters vary from place to place, and they go by many different names and images.


As a tool to encourage good behavior in children, Santa serves as the carrot, and Krampus is the stick. Krampus is the evil demon anti-Santa, or maybe his evil twin. Krampus Night is celebrated on December 5, the eve of St. Nicholas Day in Austria and other parts of Europe. Public celebrations that night have many Krampuses walking the streets, looking for people to beat. Alcohol is also involved. Injuries in recent years have led to some reforms, such as requiring all Krampuses to wear numbers so they may identified in case of overly violent behavior.

Krampus may look like a devil, or like a wild alpine beast, depending on what materials are available to make a Krampus costume. In modern times, people can spend as much as they like to become the best Krampus around—and the tradition is spreading beyond Europe. Many cities in America have their own Krampus Nights now.


Jólakötturinn is the Icelandic Yule Cat or Christmas Cat. He is not a nice cat. In fact, he might eat you. This character is tied to an Icelandic tradition in which those who finished all their work on time received new clothes for Christmas, while those who were lazy did not (although this is mainly a threat). To encourage children to work hard, parents told the tale of the Yule Cat, saying that Jólakötturinn could tell who the lazy children were because they did not have at least one new item of clothing for Christmas—and these children would be sacrificed to the Yule Cat. This reminder tends to spur children into doing their chores! A poem written about the cat ends with a suggestion that children help out the needy, so they, too, can have the protection of new clothing. It's no wonder that Icelanders put in more overtime at work than most Europeans.


Flickr // Markus Ortner

Tales told in Germany and Austria sometimes feature a witch named Frau Perchta who hands out both rewards and punishments during the 12 days of Christmas (December 25 through Epiphany on January 6). She is best known for her gruesome punishment of the sinful: She will rip out your internal organs and replace them with garbage. The ugly image of Perchta may show up in Christmas processions in Austria, somewhat like Krampus.

Perchta's story is thought to have descended from a legendary Alpine goddess of nature, who tends the forest most of the year and deals with humans only during Christmas. In modern celebrations, Perchta or a close relation may show up in processions during Fastnacht, the Alpine festival just before Lent. There may be some connection between Frau Perchta and the Italian witch La Befana, but La Befana isn't really a monster: she's an ugly but good witch who leaves presents.


A drawing of Belsnickel.
Lucas, Flickr // CC BY 2.0

Belsnickel is a male character from southwestern German lore who traveled to the United States and survives in Pennsylvania Dutch customs. He comes to children sometime before Christmas, wearing tattered old clothing and raggedy fur. Belsnickel carries a switch to frighten children and candy to reward them for good behavior. In modern visits, the switch is only used for noise, and to warn children they still have time to be good before Christmas. Then all the children get candy, if they are polite about it. The name Belsnickel is a portmanteau of the German belzen (meaning to wallop) and nickel for St. Nicholas. See a video of a Belsnickel visit here.

Knecht Ruprecht and Ru Klaas are similar characters from German folklore who dole out beatings to bad children, leaving St. Nicholas to reward good children with gifts.


Hans Trapp is another "anti-Santa" who hands out punishment to bad children in the Alsace and Lorraine regions of France. The legend says that Trapp was a real man, a rich, greedy, and evil man, who worshiped Satan and was excommunicated from the Catholic Church. He was exiled into the forest where he preyed upon children, disguised as a scarecrow with straw jutting out from his clothing. He was about to eat one boy he captured when he was struck by lightning and killed—a punishment of his own from God. Still, he visits young children before Christmas, dressed as a scarecrow, to scare them into good behavior.


The French legend of Père Fouettard, whose name translates to "Father Whipper," begins with an evil butcher who craved children to eat. He (or his wife) lured three boys into his butcher shop, where he killed, chopped, and salted them. St. Nicholas came to the rescue, resurrected the boys, and took custody of the butcher. The captive butcher became Père Fouettard, St. Nicholas' servant whose job it is to dispense punishment to bad children on St. Nicholas Day.


The Jólasveinar, or Yule Lads, are 13 Icelandic trolls, who each have a name and distinct personality. In ancient times, they stole things and caused trouble around Christmastime, so they were used to scare children into behaving, like the Yule Cat. However, the 20th century brought tales of the benevolent Norwegian figure Julenisse (Santa Claus), who brought gifts to good children. The traditions became mingled, until the formerly devilish Jólasveinar became kind enough to leave gifts in shoes that children leave out ... if they are good boys and girls. 


All the Yule Lads answer to Grýla, their mother. She predates the Yule Lads in Icelandic legend as the ogress who kidnaps, cooks, and eats children who don't obey their parents. She only became associated with Christmas in the 17th century, when she was assigned to be the mother of the Yule Lads. According to legend, Grýla had three different husbands and 72 children, all who caused trouble ranging from harmless mischief to murder. As if the household wasn't crowded enough, the Yule Cat also lives with Grýla. This ogress is so much of a troublemaker that The Onion blamed her for the 2010 eruption of the Eyjafjallajökull volcano.

A version of this post originally ran in 2013. See also: more Legendary Monsters

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84 Years Ago Today: Goodbye Prohibition!
A huge queue outside the Board of Health offices in Centre Street, New York, for licenses to sell alcohol shortly after the repeal of prohibition. The repeal of prohibition was a key policy of Franklin Roosevelt's government as it allowed the government an opportunity to raise tax revenues at a time of economic hardship.
A huge queue outside the Board of Health offices in Centre Street, New York, for licenses to sell alcohol shortly after the repeal of prohibition. The repeal of prohibition was a key policy of Franklin Roosevelt's government as it allowed the government an opportunity to raise tax revenues at a time of economic hardship.
Keystone/Getty Images

It was 84 years ago today that the Twenty-First Amendment to the Constitution was ratified, repealing the earlier Amendment that declared the manufacture, sale, and transport of alcohol illegal in the United States. Prohibition was over! Booze that had been illegal for 13 years was suddenly legal again, and our long national nightmare was finally over.

A giant barrel of beer, part of a demonstration against prohibition in America.
Henry Guttmann/Getty Images

Prohibition of alcohol was not a popular doctrine. It turned formerly law-abiding citizens into criminals. It overwhelmed police with enforcement duties and gave rise to organized crime. In cities like Milwaukee and St. Louis, the dismantling of breweries left thousands of people unemployed.

Photograph courtesy of the Boston Public Library

Homemade alcohol was often dangerous and some people died from drinking it. Some turned to Sterno or industrial alcohol, which was dangerous and sometimes poisoned by the government to discourage drinking. State and federal governments were spending a lot of money on enforcement, while missing out on taxes from alcohol.

New York City Deputy Police Commissioner John A. Leach (right) watches agents pour liquor into sewer following a raid during the height of Prohibition.

The midterm elections of 1930 saw the majority in Congress switch from Republican to Democratic, signaling a shift in public opinion about Prohibition as well as concerns about the depressed economy. Franklin Roosevelt, who urged repeal, was elected president in 1932. The Twenty-first Amendment to the Constitution was proposed by Congress in February of 1933, the sole purpose of which was to repeal the Eighteenth Amendment establishing Prohibition.

American men guarding their private beer brewing hide-out, during Prohibition.
Keystone/Getty Images

With passage of the Constitutional Amendment to repeal Prohibition a foregone conclusion, a huge number of businessmen lined up at the Board of Health offices in New York in April of 1933 to apply for liquor licenses to be issued as soon as the repeal was ratified.

The Amendment was ratified by the states by the mechanism of special state ratifying conventions instead of state legislatures. Many states ratified the repeal as soon as conventions could be organized. The ratifications by the required two-thirds of the states was achieved on December 5, 1933, when conventions in Ohio, Pennsylvania, and Utah agreed to repeal Prohibition through the Amendment.

Workmen unloading crates of beer stacked at a New York brewery shortly after the repeal of Prohibition.
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A brewery warehouse in New York stacked crates past the ceiling to satisfy a thirsty nation after the repeal of Prohibition.

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Liquor wouldn't officially be legal until December 15th, but Americans celebrated openly anyway, and in most places, law enforcement officials let them.


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