Argument from ignorance

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

Argument from ignorance (Latin : argumentum ad ignorantiam), or appeal to ignorance, ^[a] 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. ^{[1] [2]} 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. ^{[3] [4]}

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: ^[5]

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

Logic

The argument has the form:

${\displaystyle \neg P}$ has not been proven true.
Therefore, ${\displaystyle P}$ is true. ^[5]

Its reverse:

${\displaystyle P}$ has not been proven true.
Therefore, ${\displaystyle \neg P}$ is true.

where ${\displaystyle P}$ 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." ^[6]
• 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:

"Simply because you do not have evidence that something exists does not mean that you have evidence that it doesn't exist." ^{[7] [b]}

• The aphorism "No news is good news". ^[8] The usefulness of this as a heuristic may vary by context.
• Carl Sagan explains in his book The Demon-Haunted World :

Appeal to ignorance: the claim that whatever has not been proved false must be true, and vice versa. (e.g., There is no compelling evidence that UFOs are not visiting the Earth; therefore, UFOs exist, and there is intelligent life elsewhere in the Universe. Or: There may be seventy kazillion other worlds, but not one is known to have the moral advancement of the Earth, so we're still central to the Universe.) This impatience with ambiguity can be criticized in the phrase: absence of evidence is not evidence of absence. ^[9]

Job call example

They never called me back. I guess I didn't get the job. ^[10]

This would follow the second form of the argument:

${\displaystyle P}$ (I got the job) has not been proven true (via lack of callback).
Therefore, ${\displaystyle \neg P}$ (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

See also: Autoepistemic logic

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

• Philosophy portal

• Argument from silence  – Argument based on the absence of statements in historical documents, rather than their presence
• Hitchens's razor  – General rule rejecting claims made without evidence
• List of fallacies
• Martha Mitchell effect  – Labelling real experiences as delusional
• Occam's razor  – Philosophical problem-solving principle
• Precautionary principle  – Risk management strategy
• Russell's teapot  – Analogy devised by Bertrand Russell

Notes

1. "Ignorance" represents "a lack of contrary evidence".
2. Though the authors here caution that this may not be an entirely appropriate use of the argument as the onus of providing proof for a substantive statement, like "there are WMDs in Iraq", lies with the party making the claim, not with those opposing it.

References

1. Copi, Irving M (2016). Introduction to logic (14th ed.). Routledge Publication. p. 146. ISBN   9780205820375.
2. Hurley, Patrick J (2012). A Concise Introduction to Logic (11th ed.). Boston, Mass.: Cengage Learning. p. 140. ISBN   9780840034175.
3. Hansen, Hans V.; Pinto, Robert C., eds. (1995). Fallacies: Classical and Contemporary Readings. University Park, Pa.: Pennsylvania State University Press. ISBN   978-0271014166. OCLC   30624864.
4. Locke, John (1690). "Book IV, Chapter XVII: Of Reason". An Essay Concerning Human Understanding. Retrieved 12 March 2015.
5. Walton, Douglas (1996). Arguments from Ignorance. University Park, PA: Pennsylvania State University Press. ISBN   0-271-01474-1.
6. Bennett, Bo. "Argument from Ignorance". www.LogicallyFallacious.com. Retrieved 23 November 2016.
7. Brown, Deborah; Key, Brian (22 April 2019). "You look but do not find: why the absence of evidence can be a useful thing". The Conversation. Archived from the original on 15 June 2021. Retrieved 20 June 2022.
8. Daily Kos. "Logical Fallacies Bootcamp: Appeal to Ignorance".
9. Sagan, Carl. "Chapter 12: The Fine Art of Baloney Detection". The Demon-Haunted World.
10. "Appeal to Ignorance". Department of Philosophy - Texas State University.

Further reading

• Hansen, Hans V.; Pinto, Robert C. Fallacies: classical and contemporary readings.
• Copi, Irving M; Cohen, Carl (2010). Introduction to Logic (14th ed.). Routledge. ISBN   978-0205820375. OCLC   862726425.
• Walton, D. (1992). "Nonfallacious Arguments From Ignorance" (PDF). American Philosophical Quarterly. 29 (4): 381–387.
• Walton, D. (2010). Arguments from Ignorance. Pennsylvania State University Press. ISBN   978-0-271-04196-4.
• Alton, Douglas G.; Bland, J. Martin (1995). "Absence of evidence is not evidence of absence". BMJ. 311 (7003): 485. doi:10.1136/bmj.311.7003.485. PMC   2550545 . PMID   7647644.

External links

• Fallacy Files – article on Appeal to Ignorance