Argument from ignorance

File:John Locke by John Greenhill.jpg

John Locke (1632–1704), the likely originator of the term.

Argument from ignorance (Template:Langx), or appeal to ignorance,Template:Efn is an informal fallacy where something is claimed to be true or false because of a lack of evidence to the contrary.

The fallacy is committed when one 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. If a proposition has not yet been proven true, one is not entitled to conclude, solely on that basis, that it is false, and if a proposition has not yet been proven false, one is not entitled to conclude, solely on that basis, that it is true.<ref>Template:Cite book</ref><ref>Template:Cite book</ref> Another way of expressing this is that a proposition is true only if proven true, and a proposition is false only if proven false. If no proof is offered (in either direction), then the proposition can be called unproven, undecided, inconclusive, an open problem or a conjecture.

Use

The term was likely coined by philosopher John Locke in the late 17th century.<ref>Template:Cite book</ref><ref>Template:Cite book</ref>

In debates, appealing to ignorance is sometimes an attempt to shift the burden of proof.

There is a debate over whether the argument from ignorance is always fallacious. It is generally accepted that there are only special circumstances in which this argument may not be fallacious. For example, with the presumption of innocence in legal cases, it would make sense to argue:<ref name="Walton1996">Template:Cite book</ref>

It has not been proven that the defendant is guilty.
Therefore, the defendant is not guilty.

Logic

The argument has the form:

<math>\neg P</math> has not been proven true.
Therefore, <math>P</math> is true.<ref name="Walton1996" />

Its reverse:

<math>P</math> has not been proven true.
Therefore, <math>\neg P</math> is true.

where <math>P</math> is a proposition, i.e. a statement declaring that something is true, or that it is false.

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 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, 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."<ref>{{#invoke:citation/CS1|citation

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• 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:

• The aphorism "No news is good news".<ref>{{#invoke:citation/CS1|citation

|CitationClass=web }}</ref> The usefulness of this as a heuristic may vary by context.

• Carl Sagan explains in his book The Demon-Haunted World:

Job call example

They never called me back. I guess I didn't get the job.<ref>{{#invoke:citation/CS1|citation

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}}</ref>

This would follow the second form of the argument:

<math>P</math> (I got the job) has not been proven true (via lack of callback).
Therefore, <math>\neg P</math> (I didn't get the job) is true.

While both parts may be true (in this case, you actually didn't get the job), the reasoning is fallacious because there are cases, even if unlikely, where you could get the job, but don't receive a callback. For example, administrative delays, technical issues, or some kind of oversight from the hiring team.

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

Template:See also Arguments from self-knowing take the form:

1. If P were true then I would know it; in fact I do not know it; therefore P cannot be true.
2. 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 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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Further reading

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External links

• Fallacy Files – article on Appeal to Ignorance