Appeal to Ignorance

This is also known as Argumentum ad ignorantiam.

This is a fallacy that says, you can't disprove my belief, therefore it's true. Often it is phrased more carefully such as If you can't disprove what I believe, I'm free to believe it's true.

Examples

Our god's existence hasn't been disproven, therefore he/she exists.

You haven't disproven they are out to get you, therefore they are.

You haven't disproven that you and your family aren't plotting against the King Queen Fuhrer, therefore you are. Off to prison!

The cop says, you haven't proven you're innocent, so I'm going to ask you 100 wildly speculative questions until you demand to be released due to lack of evidence.

You haven't disproven that Bob is gay or a Commie or a liberal (or anything else we don't like), therefore he is.

Weaknesses

In each case, you merely need to point out that just because someone else hasn't disproven a claim, that does not make it true.

• It may be disproved in future.
• It may have been disproved already but the arguer does not know it.
• It may be something that cannot be either proved or disproved.

In the case of a person who claims the existence of the Christian/Jewish/Muslim god, simply because his existence is not disproven, often has not thought it through. Point out to them, there is an infinite number of claims that are not disproven, but that is not sufficient to think they are true.

• It has not been disproven that Thor, Odin, Freya, Loki or any other Norse god exists.
• It has not been disproven that Zeus, Juno, Vulcan, Neptune or any other Roman god exists.
• It has not been disproven that you need to believe in made-up stories to escape your miserable life.

If the arguer is clearly trying to slander someone, like by alleging Jane may be a lesbian because no one's disproven it, point that out. Ask why really does the slanderer dislike the victim, and point out the slanderer's lack of bravery in speaking behind the victim's back. It is often merely that the victim is competitively superior to the slanderer:

• The slanderer being stupid
• The slanderer being unattractive
• The slanderer being untalented
• The slanderer feeling entitled i.e. expecting success without effort

... hence the slander.

In the case of frequent insinuation and slander, ask, do they exist in a subculture where trash talk is an addictive pastime or is even elevated to a sport? Ask them, what depth will they not sink to?

Oftentimes an insinuator will assume that some claim P is true about a person not because it's not disproven, because it applies to the insinuator. This is called psychological projection: Assigning traits to others that you yourself possess and and about which you feel shameful. For instance, so-called straight men who insist that other men are gay are usually secretly gay or bisexual.