Argument from ignorance (from la, argumentum ad ignorantiam), also known as appeal to ignorance (in which ''ignorance'' represents "a lack of contrary evidence"), is a
fallacy in informal logic
Informal fallacies are a type of incorrect argument in natural language. The source of the error is not just due to the ''form'' of the argument, as is the case for formal fallacies, but can also be due to their ''content'' and ''context''. Fallac ...
. It asserts that a proposition is true because it has not yet been proven false or a proposition is false because it has not yet been proven true. This represents a type of
false dichotomy in that it excludes the possibility that there may have been an insufficient investigation to prove that the proposition is either true or false.
It also does not allow for the possibility that the answer is
unknowable, only
knowable in the future, or neither completely true nor completely false. In debates, appealing to ignorance is sometimes an attempt to shift the
burden of proof. The term was likely coined by philosopher
John Locke
John Locke (; 29 August 1632 – 28 October 1704) was an English philosopher and physician, widely regarded as one of the most influential of Enlightenment thinkers and commonly known as the "father of liberalism". Considered one of ...
in the late 17th century.
Examples
* "I take the view that this lack (of enemy subversive activity in the west coast) is the most ominous sign in our whole situation. It convinces me more than perhaps any other factor that the sabotage we are to get, the
Fifth Column
A fifth column is any group of people who undermine a larger group or nation from within, usually in favor of an enemy group or another nation. According to Harris Mylonas and Scott Radnitz, "fifth columns" are “domestic actors who work to un ...
activities are to get, are timed just like Pearl Harbor ... I believe we are just being lulled into a false sense of security." –
Earl Warren
Earl Warren (March 19, 1891 – July 9, 1974) was an American attorney, politician, and jurist who served as the 14th Chief Justice of the United States from 1953 to 1969. The Warren Court presided over a major shift in American constitutio ...
, then California's Attorney General (before a congressional hearing in San Francisco on 21 February 1942).
* This example clearly states what appeal to ignorance is: "Although we have proven that the moon is not made of spare ribs, we have not proven that its core cannot be filled with them; therefore, the moon’s core is filled with spare ribs."
*
Donald Rumsfeld, then
US Secretary of Defense, argued against the argument from ignorance when discussing the
lack of evidence for WMDs in Iraq prior to the invasion:
*
Carl Sagan
Carl Edward Sagan (; ; November 9, 1934December 20, 1996) was an American astronomer, planetary scientist, cosmologist, astrophysicist, astrobiologist, author, and science communicator. His best known scientific contribution is research on ex ...
explains in his book ''
The Demon-Haunted World'':
Related terms
Contraposition and transposition
Contraposition is a logically valid rule of inference that allows the creation of a new proposition from the negation and reordering of an existing one. The method applies to any proposition of the type ''If A then B'' and says that negating all the variables and switching them back to front leads to a new proposition i.e. ''If Not-B then Not-A'' that is just as true as the original one and that the first implies the second and the second implies the first.
Transposition is exactly the same thing as Contraposition, described in a different language.
Null result
''
Null result'' is a term often used in science to indicate ''evidence of absence''. A search for water on the ground may yield a null result (the ground is dry); therefore, it probably did not rain.
Related arguments
Argument from self-knowing
Arguments from self-knowing take the form:
# If P were true then I would know it; in fact I do not know it; therefore P cannot be true.
# If Q were false then I would know it; in fact I do not know it; therefore Q cannot be false.
In practice these arguments are often unsound and rely on the truth of the supporting
premise. For example, the claim that ''If I had just sat on a wild
porcupine
Porcupines are large rodents with coats of sharp spines, or quills, that protect them against predation. The term covers two families of animals: the Old World porcupines of family Hystricidae, and the New World porcupines of family, Erethiz ...
then I would know it'' is probably not fallacious and depends entirely on the truth of the first premise (the ability to know it).
See also
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Notes
References
Further reading
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External links
Fallacy Files– article on Appeal to Ignorance
{{DEFAULTSORT:Argument From Ignorance
Relevance fallacies
Ignorance
Barriers to critical thinking