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The duck test is a form of abductive reasoning. This is its usual expression:
If it looks like a duck, swims like a duck, and quacks like a duck, then it probably is a duck.
The test implies that a person can identify an unknown subject by observing that subject's habitual characteristics. It is sometimes used to counter abstruse arguments that something is not what it appears to be.
In 1738 a French automaton maker invented a mechanical duck, and accidentally created false abductive reasoning still in use today. [1] . Jacques de Vaucanson was a famous inventor who created an automaton that was a mechanical duck. The robotic duck would quack, move its head to eat some grain which would appear to digest and after a short time, would discharge a mixture that looked and smelled like duck droppings. The irony is that while the phrase is often cited, even by leading figures, as abductive reasoning proof, in fact it can be wrong, just as its origin proved it entertaining, but wrong. It ate, quacked and excreted like a duck, but in fact was an 18th century mechanical robot.
The examples and perspective in this section deal primarily with the United States and do not represent a worldwide view of the subject.(April 2024) |
Indiana poet James Whitcomb Riley (1849–1916) may have coined the phrase when he wrote:
When I see a bird that walks like a duck and swims like a duck and quacks like a duck, I call that bird a duck. [2]
A common variation of the wording of the phrase may have originated much later with Emil Mazey, secretary-treasurer of the United Auto Workers, at a labor meeting in 1946 accusing a person of being a communist:
I can't prove you are a Communist. But when I see a bird that quacks like a duck, walks like a duck, has feathers and webbed feet and associates with ducks—I'm certainly going to assume that he is a duck. [3]
The term was later popularized in the United States by Richard Cunningham Patterson Jr., United States ambassador to Guatemala in 1950 during the Cold War, who used the phrase when he accused Guatemala's Jacobo Arbenz Guzmán government of being Communist. Patterson explained his reasoning as follows:
Suppose you see a bird walking around in a farm yard. This bird has no label that says 'duck'. But the bird certainly looks like a duck. Also, he goes to the pond and you notice that he swims like a duck. Then he opens his beak and quacks like a duck. Well, by this time you have probably reached the conclusion that the bird is a duck, whether he's wearing a label or not. [4]
Later references to the duck test include Cardinal Richard Cushing's, who used the phrase in 1964 in reference to Fidel Castro. [5] [6]
Douglas Adams parodied this test in his book Dirk Gently's Holistic Detective Agency :
If it looks like a duck, and quacks like a duck, we have at least to consider the possibility that we have a small aquatic bird of the family Anatidae on our hands. [7]
Monty Python also referenced the test in the Witch Logic scene in their 1975 film Monty Python and the Holy Grail :
[Bedevere:] There are ways of telling whether she is a witch! [Villagers:] Are there? What? Tell us, then! Tell us! [B:] Tell me. What do you do with witches? [Vs:] Burn! Burn! You burn them! Burn! [B:] And what do you burn apart from witches? [Vs:] More witches! Wood! [B:] So, why do witches burn? [Villager:] 'Cos they're made of wood? [B:] Good! ... So; how do we tell if she is made of wood? [V:] Build a bridge out of 'er! [B:] Ah, but can you not also make bridges out of stone? [Vs:] Oh yeah. [B:] Does wood sink in water? [Vs:] No, it floats! Throw her into the pond! Yaa! [B:] What also floats in water? [Vs:] Bread! Apples! Very small rocks? Cider! Gra-Gravy! Cherries! Mud! Churches? Churches! Lead! Lead! [King Arthur:] A duck! [Vs:] Ooh! [B:] Exactly. So, logically... [V:] If she weighs the same as a duck, she's made of wood... [B:] and therefore... [V:] a witch! [8]
In 2015, a variation of the duck test was applied in the revocation of tax exempt "nonprofit" status to Blue Shield of California:
In a startling blow to one of California's biggest health insurers, the state has revoked the tax-exempt status of Blue Shield of California, forcing the company to pay tens of millions of dollars in back taxes and unleashing a torrent of calls for it to return billions of dollars to customers. The tax board's action 'was an acknowledgment of what Blue Shield was already doing, or not doing,' said Anthony Wright, head of Health Access California, a consumer advocacy group. 'And if it looks like a duck and talks like a duck, it should be taxed like a duck. [9]
The Liskov Substitution Principle in computer science is sometimes expressed as a counter-example to the duck test:
If it looks like a duck and quacks like a duck but it needs batteries, you probably have the wrong abstraction. [10]
Russian Minister of Foreign Affairs Sergey Lavrov used a version of the Duck Test in 2015 in response to allegations that Russian airstrikes in Syria were not targeting terrorist groups, primarily ISIS, but rather West-supported groups such as the Free Syrian Army. When asked to elaborate his definition of 'terrorist groups', he replied:
If it looks like a terrorist, if it acts like a terrorist, if it walks like a terrorist, if it fights like a terrorist, it's a terrorist, right? [11]
Professor Vladimir Vapnik, a pioneer and co-inventor of Support Vector Machines (SVM) and a major contributor to the theory of machine learning and many foundational ideas in statistical learning, uses the duck test as a way to summarize the importance of simple predicates to classify things. [12] During the discussion he often uses the test to illustrate that the concise format of the duck test is a form of intelligence that machines are not capable of producing.
The philosopher Slavoj Žižek has cited the Marx Brothers' rewording of the duck test: "He may look like an idiot and talk like an idiot, but don't let that fool you. He really is an idiot." The humorousness of this line lies in its violation of an expected opposite.
Similarly, the term elephant test refers to situations in which an idea or thing, "is hard to describe, but instantly recognizable when spotted". [13]
The term is often used in legal cases when there is an issue which may be open to interpretation, [14] [15] such as in the case of Cadogan Estates Ltd v Morris, when Lord Justice Stuart-Smith referred to "the well known elephant test. It is difficult to describe, but you know it when you see it", [16] and in Ivey v Genting Casinos , when Lord Hughes (in discussing dishonesty) opined "like the elephant, it is characterised more by recognition when encountered than by definition." Overruling in part R v Ghosh. [17]
A similar incantation (used however as a rule of exclusion) was invoked by the concurring opinion of Justice Potter Stewart in Jacobellis v. Ohio , 378 U.S. 184 (1964), an obscenity case. He stated that the Constitution protected all obscenity except "hard-core pornography". Stewart opined, "I shall not today attempt further to define the kinds of material I understand to be embraced within that shorthand description; and perhaps I could never succeed in intelligibly doing so. But I know it when I see it, and the motion picture involved in this case is not that."
Monty Python's Life of Brian is a 1979 British comedy film starring and written by the comedy group Monty Python. It was directed by Jones. The film tells the story of Brian Cohen, a young Jewish-Roman man who is born on the same day as—and next door to—Jesus, and is subsequently mistaken for the Messiah.
Monty Python were a British comedy troupe formed in 1969 consisting of Graham Chapman, John Cleese, Terry Gilliam, Eric Idle, Terry Jones, and Michael Palin. The group came to prominence for the sketch comedy series Monty Python's Flying Circus, which aired on the BBC from 1969 to 1974. Their work then developed into a larger collection that included live shows, films, albums, books, and musicals; their influence on comedy has been compared to the Beatles' influence on music. Their sketch show has been called "an important moment in the evolution of television comedy".
The "Dead Parrot Sketch", alternatively and originally known as the "Pet Shop Sketch" or "Parrot Sketch", is a sketch from Monty Python's Flying Circus about a non-existent species of parrot, called a "Norwegian Blue". A satire on poor customer service, it was written by John Cleese and Graham Chapman and initially performed in the show's first series, in the eighth episode.
Monty Python and the Holy Grail is a 1975 British comedy film satirizing the Arthurian legend, written and performed by the Monty Python comedy group and directed by Gilliam and Jones in their feature directorial debuts. It was conceived during the hiatus between the third and fourth series of their BBC Television series Monty Python's Flying Circus.
Eric Idle is an English actor, comedian, songwriter, musician, screenwriter and playwright. He was a member of the British comedy group Monty Python and the parody rock band the Rutles. Idle studied at Pembroke College, Cambridge, and joined Cambridge University Footlights. He reached stardom when he co-created and acted in the sketch series Monty Python's Flying Circus (1969–1974) and the films Monty Python and the Holy Grail (1975), Life of Brian (1979) and The Meaning of Life (1983) with John Cleese, Michael Palin, Terry Gilliam, Terry Jones, and Graham Chapman.
"The Lumberjack Song" is a comedy song by the comedy troupe Monty Python. The song was written and composed by Terry Jones, Michael Palin, and Fred Tomlinson.
Neil James Innes was an English writer, comedian and musician. He first came to prominence in the pioneering comedy rock group Bonzo Dog Doo-Dah Band and later became a frequent collaborator with the Monty Python troupe on their BBC television series and films, and is often called the "seventh Python" along with performer Carol Cleveland. He co-created the Rutles, a Beatles parody/pastiche project, with Python Eric Idle, and wrote the band's songs. He also wrote and voiced the 1980s ITV children's cartoon adventures of The Raggy Dolls.
And Now for Something Completely Different is a 1971 British sketch comedy film based on the television comedy series Monty Python's Flying Circus featuring sketches from the show's first two series. The title was taken from a catchphrase used in the television show.
"Rubber Duckie" is a song sung by the Muppet character Ernie on Sesame Street. The song is named after Ernie's toy, a rubber duck affectionately named Rubber Duckie.
Spamalot is a stage musical with score by John Du Prez and Eric Idle, with lyrics and book by Idle. Based on the 1975 film Monty Python and the Holy Grail, the musical offers a highly irreverent parody of Arthurian legend.
"Candid Photography", better known as "Nudge Nudge", is a sketch from the third Monty Python's Flying Circus episode, "How to Recognise Different Types of Trees From Quite a Long Way Away" featuring Eric Idle and Terry Jones as two strangers who meet in a pub.
Mr. Creosote is a fictional character who appears in Monty Python's The Meaning of Life. He is a monstrously obese and vulgar restaurant patron who is served a vast amount of food and alcohol whilst vomiting repeatedly. After being persuaded to eat an after-dinner mint – "It's only wafer-thin" – he graphically explodes. The sequence opens the film's segment titled "Part VI: The Autumn Years".
QuackShot Starring Donald Duck, released in Japan as QuackShot Gurujia-ō no Hihō, is a 1991 platforming video game developed and published by Sega for the Sega Genesis. The game was released in Europe in 1991, in North America on December 19, 1991, and in Japan the following day. QuackShot stars Donald Duck and his three nephews, Huey, Dewey, and Louie, as treasure-hunters. The game was influenced by the Indiana Jones film series.
Michael Palin's Hemingway Adventure is a 1999 BBC television documentary presented by Michael Palin. It records Palin's travels as he visited many sites where Ernest Hemingway had been. The sites include Spain, Chicago, Paris, Italy, Africa, Key West, Cuba, and Idaho.
Hartlaub's duck is a dark chestnut-coloured duck of African forests. Formerly included in the paraphyletic "perching duck" assemblage, it was later moved to the dabbling duck assemblage. However, it is fairly distinct from the "typical" dabbling ducks, and is placed in the monotypic genus Pteronetta to reflect this.
The phrase "I know it when I see it" is a colloquial expression by which a speaker attempts to categorize an observable fact or event, although the category is subjective or lacks clearly defined parameters. It has been a common expression since at least the 19th century. A similar phrase appears in Arthur Conan Doyle's "The Hound of the Baskervilles," in which Sherlock Holmes comments on the quality of a portrait by stating "I know what is good when I see it." The phrase was used in 1964 by United States Supreme Court Justice Potter Stewart to describe his threshold test for obscenity in Jacobellis v. Ohio. In explaining why the material at issue in the case was not obscene under the Roth test, and therefore was protected speech that could not be censored, Stewart wrote:
I shall not today attempt further to define the kinds of material I understand to be embraced within that shorthand description ["hard-core pornography"], and perhaps I could never succeed in intelligibly doing so. But I know it when I see it, and the motion picture involved in this case is not that.
"Dirty Hungarian Phrasebook" is a Monty Python sketch. It first aired in 1970 on Monty Python's Flying Circus as part of Episode 25, and also appears in the film And Now for Something Completely Different. Atlas Obscura has noted that it may have been inspired by English as She Is Spoke, a 19th-century Portuguese–English phrase book regarded as a classic source of unintentional humour, as the given English translations are generally completely incoherent.
Absolutely Anything is a 2015 British science fantasy comedy film directed by Terry Jones, and written by Terry Jones and Gavin Scott. It stars Simon Pegg, Kate Beckinsale, Sanjeev Bhaskar, Rob Riggle, Eddie Izzard and Joanna Lumley, with the nonhuman characters' voices provided by John Cleese, Terry Gilliam, Eric Idle, Jones, Michael Palin and Robin Williams. It was the first movie to feature all living Monty Python members since Monty Python's The Meaning of Life (1983), and the first without Graham Chapman, who died in 1989. Principal photography and production began on 24 March 2014 and ended on 12 May that year. The film was released in the United Kingdom on 14 August 2015 by Lionsgate UK, and in the United States on 12 May 2017, grossing $6.3 million worldwide.
Monty Python's Cow Tossing is a catapult-physics game. It was developed by South African studio Luma Arcade and released by Zed Worldwide on February 3, 2011 for Android, iOS, and J2ME. The game is similar in style to Angry Birds and Crush the Castle, and includes the premise of firing cows at Englishmen who are located in structures built of concrete, wood, and other materials. It is based on the film Monty Python and the Holy Grail "in which French militiamen hurl a heifer onto a band of English relic seekers", and to further tie-in to the movie, "funny quotes from the movie appear in bubbles over the characters".