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WillowOne's Positions

Duck Test

"If it looks like a duck, swims like a duck, and quacks like a duck, then it probably is a duck."

Overview

The duck test is a rule for inferring what something is from what it observably does. If a thing has all the observable properties of a duck, the reasonable conclusion is that it is a duck, whatever it calls itself; and conversely, a thing that calls itself a duck but neither swims nor quacks is not one. It is a form of abductive reasoning, inference to the best explanation of the evidence, and its force comes from the fact that we have no access to the "real nature" of anything except through its behaviour.

The phrase is widely attributed to the American poet James Whitcomb Riley (1849–1916), who is said to have written: "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." No confirmed source in Riley's work has been found. The expression was in general use by the mid-twentieth century; Richard Cunningham Patterson Jr., the United States ambassador to Guatemala, used "the duck test" in 1950 to argue that the Árbenz government was communist whatever it said about itself.

Notes

  • The test is a counter to the demand for essences. Asked whether a system "really" understands, whether a medium "really" has a gift, or whether a practice "really" is a religion, the duck test says: look at what it does. If a cold reader and a psychic produce the same results by the same observable methods, the test says they are the same thing (Psychics and Mediums).
  • It cuts both ways. It is the argument by which a label is refused to something that fails the behavioural tests, and the argument by which a label is applied to something that passes them, whatever its self-description. It is close to Functionalism in the philosophy of mind: a state is what it does.
  • It is probabilistic, not conclusive. The inference is to the most likely explanation, and a determined deceiver can imitate a duck. Think Horses, Not Zebras is the same reasoning stated for diagnosis; Occam's Razor is the general principle behind both.

Also see

Wikipedia: https://en.wikipedia.org/wiki/Duck_test