Defending a claim by saying that it cannot be proven because the evidence is being hidden from the public. This is a fallacy called conspiracy theory, also known as canceling hypothesis fallacy. It’s associated with conspiracy theorists because this kind of claim is mainly made by them.
This kind of reasoning blocks the argument from moving towards a productive end. When the speaker’s claim is attacked, the argument is shifted into a debate about the existence of evidence. There is no way to battle this kind of an argument except pointing out the fallacy, which also rarely works.
Example 1:
“Lee Oswald did not kill John F. Kennedy. I could prove my claim but the government hid and destroyed evidence deliberately.”
Example 2:
“At the head of every kind of government there is a secret society. Of course, I cannot prove this because the same societies make sure that the truth stays hidden.”
Example 3:
Person A: “The Catholic Church is associated with the Devil.”
Person B: “That’s a preposterous claim. Can you present any evidence”
Person A: “Everything happens behind closed doors and any evidence is destroyed. The fact that they are hiding things just makes me more sure.”
As is evident, the speaker makes a claim and then makes it immune from any attack by saying that there is no way to present any proof. This kind of reasoning becomes dangerous when the hidden evidence is taken as proof, as is the case in Example 3.
The canceling hypothesis fallacy is common with whistleblowers. The most famous case is with Bob Lazar and his work with alien aircraft. Although Bob Lazar is an educated and a reliable person, his claims cannot be taken with certainty because of this fallacy. Disappointment can be noticed in Mr. Lazar because the only way he can support his claim is with this kind of reasoning.