Duck Test

The duck test is a frequently cited colloquial example of abductive reasoning. Its usual expression is:

The test implies that a person can identify an unknown subject by observing that subject's habitual characteristics. It is sometimes used to counter abstract arguments that something might not be what it appears to be.

Notable uses

Indiana poet James Whitcomb Riley (1849–1916) may have coined the phrase when he wrote:

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:

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:

Later references to the duck test include Cardinal Richard Cushing's, who used the phrase in 1964 in reference to Fidel Castro.

Douglas Adams parodied this test in his book ''Dirk Gently's Holistic Detective Agency'':

Monty Python referenced the test in the Witch Logic scene in their 1975 film ''Monty Python and the Holy Grail'', where a mob of villagers reason that because witches burn, they must be made of wood, which floats in water, and since ducks also float in water:

In 2015, a variation of the duck test was applied in the revocation of tax exempt "nonprofit" status to Blue Shield of California:

The Liskov Substitution Principle in computer science is sometimes expressed as a counter-example to the duck test:

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:

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. 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 frequently references the Marx Brothers' rewording of the duck test in '' Duck Soup'': "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.

Elephant test

Similarly, the term ''elephant test'' refers to situations in which an idea or thing, "is hard to describe, but instantly recognizable when spotted".

The term is often used in legal cases when there is an issue which may be open to interpretation, 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", 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.Ivey v Genting Casinos (UK) Ltd t/a Crockfords
017UKSC 67 (25 Oct 2017) (at paragraph 48)

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."

See also

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References

Further reading

* {{Citation, first1=Howard Chandler , last1=Christy , last2=Betts , first2=Ethel Franklin , title=The complete works of James Whitcomb Riley , year=1982

English-language idioms
Epistemology
Razors (philosophy)
Heuristics
Metaphors referring to birds
Articles containing video clips
Ducks in popular culture