The arguer asserts either

a.That a claim must be true because no one has proven it false, or

b.That a claim must be false because no one has proven it true.


There is no evidence against P. Therefore, P.

There is no evidence for P. Therefore, not P.


This ad for John McCain, "Ladies and Gentlemen," commits the fallacy of appeal to ignorance.

image from clip

The ad seems to claim that because we don't know Obama won't be tested, he necessarily will be.

In this ad, produced by the McCain campaign, features Joe Biden speaking about Barrack Obama: “Mark my words it will not be six months until the world will test Barrack Obama. The world is looking; we’re going to have an international crisis to test the metal of this guy. I guarantee you it’s going to happen.” He is really appealing to our necessary ignorance of the future: we cannot know what will happen if and when Obama becomes president; we ertainly do not know that he won't be"tested." Therefore, we must assume that he will be.

Other Examples Edit


This ad for Reefer Madness, commits the fallacy of appeal to ignorance. The claim that marijuana is bad must be true because no one has provenit false. Debuting in 1936, Reefer Madness was a morality tale. At the time, the majority of people were not yet familiar with the drug; this film was intended to get to public before the public got to“marijuana. A few years later RM would be re-released with the title Tell Your Children, in an attempt to get parents to warn their children of the dangers of reefer. With wide circulation, the stories told in the movie became widely accepted. People believed that if they were to get high they may hack someone to death, rape someone, or even kill themselves. Mind you, the majority of the public had no preconceptions of the effects of marijuana. For this reason, this clip exhibits that the movie’s intent was to appeal to the ignorance of the public.

This ad, "1976 Swine Flu Propaganda" for the swine flu shot commits the fallacy of appeal to ignorance.


If there is an appeal to ignorance here, it runs, "We do not know that the swine flu isn't coming; therefore, it is coming." The narrator intones, "A swine flu epidemic may be coming." We then see a man, a truck driver, who had just protested that he didn't need a shot miserably sick in bed. The narrator goes on: "It could make you very sick." Another protester, this time an older woman, falls. It seems, though, that this ad might be making a milder -- non-fallacious -- claim: We don't know that swine flu isn't coming; therefore, it coud well come and it's better to be prepared."

This ad against the 1984 re-election of Ronald Reaga, "1984 Democratic Presidential Advertisement" commits the fallacy of appeal to ignorance.


The ad seems to assert that we have no evidence Reagan won't send the economy into a downturn; therefore, Reagan will send the economy into a downturn.

This ad shows a roller coaster climbing. At the end of the ad (0:22), the roller coaster reaches the summit of its climb. The viewer is supposed to understand that the roller coaster represents the nation's economy: with Reagan as president the economy will go up...up...up. The inevitable sequel of the climb is the chute. The narrator delivers the punch line: "If you're thinking of voting for Ronald Reagan in 1984, think of what will happen in 1985."

This ad for Proposition 8, "Yes on 8 TV Ad: Whether You Like It Or Not," commits the fallacy of appeal to ignorance.

Gavin newsom
This video for Proposition 8, which bans gay marriages, begins with a clip of San Francisco Mayor Gavin Newsom delivering a speech during the Gay Marriage Press Conference on May 15, 2008. Mayor Newsom, who supports the rights of gay citizens, makes a prediction that gay marriage will be legalized. The ad, for Prop 8, includes the clip of Newsome in order to alarm voters. The ad asserts that, if Prop 8 fails, people will not only have to tolerate same-sex marriage, but support it, as well. According to this advertisement, four Californian judges ignored four million voters and “imposed same sex marriage.”� At the end of the video, Professor Richard Peterson of Pepperdine University School of Law predicts that, if Prop 8 fails, opponents of gay marriage will be prosecuted for their beliefs and will have to suffer gay marriage being taught in schools. The video ends with a repetition of Newsom’s “whether you like it or not."
Paterson commits an appeal to ignorance in argung, albeit implicitly, that, as we don't know that people will not be prosecuted for their beliefs, we must assume that they will. If Newsom also appeals to ignorance it is in arguing, albeit implicitly, that because we don't have any evidence that Prop 8 will pass, we must conclude that it won't.

McCarthyism Pokemon Theme song

This video describes McCarthyism to the tune of the Pokemon theme song. It gives an account of McCarthy's Communist witch hunt. McCarthy put every American at risk of being not only accused of being a Communist, but convicted of it as well. McCarthy's "logic" ran: If there is no evidence that someone is not a Communist, we must conclude that they are." The song in the video includes lyrics such as, “Each citizen must understand the threat that lies inside . . . they aren’t our friends…we’ll follow and we’ll pull through…we’ll win this fight.” The chorus is “Gotta catch ‘em all.” The video brings out other fallacies McCArthy committed -- not only appeal to ignorance, but also appeal to the people (he rallies all to support “the fight”) and fear tactics (threatening “they’re all around us”).

This ad discussing McCarthyism, "McCarthy Communist Hearings," commits the fallacy of appeal to ignorance.

Philip jessup
This video discusses McCarthyism, otherwise known as the Red Scare. Senator Joseph McCarthy was notorious for, without proof, accusing individual Americans of being Communists. His most famous allegations regarded ten Hollywood celebrities and a list of an estimated two hundred people in government. This video features Philip Jessup, a New York jurist, speaking before the Tydings Committee in 1950. Jessup points out that McCarthy does not have “the slightest iota of proof" that he, Jessup, "has an unusual affinity for Communist causes.”
Jessup might also be said to commit an appeal to ignorance in stating that because there is no proof that he is a Communist, it must be concluded that he is not.

These characters from a clip from Pirates of the Carribbean: Curse of the Black Pearl (2:40-3:34), commits the fallacy of appeal to ignorance.

Royal Navy guards Murtogg and Mullroy argue over the existence of the Black Pearl. Mullroy does not believe the Black Pearl exists, while Murtogg insists that it exists because he has seen it. Mullroy attacks the truth of whether Murtogg has not seen a ship that is “crewed by the damned and captained by a man so evil that Hell itself spat him back out” in order to disprove whether Mullroy has seen the ship. Since Mullroy gets Murtogg to agree that he has not seen a ship that matches all the criteria for the Black Pearl, he concludes that the Black Pearl must not exist. Mullroy commits an appeal to ignorance in arguing that because Mulroy has not seen it, the Black Pearl does not exist.