"No one has ever been able to prove that psychic powers do not exist.…

Concept — Some arguments fail because of what their premises are actually about: they report the state of our evidence rather than the state of the world. In logic, the fact that a proposition has never been established says nothing about whether it is true, and the fact that it has never been refuted says nothing either. Absence of proof is not proof of absence, and absence of disproof is not proof.

Application — the argument in the stem is analysed step by step.

1. Read the premise: nobody has succeeded in proving that psychic powers do not exist. This reports only what has not been established; it says nothing about the world itself.

2. Read the conclusion: psychic powers do exist. This asserts a definite truth value about the world.

3. Test the link: the sole ground offered is the failure of an opposing proof. The argument therefore travels from "not disproved" to "true", that is, from a gap in the available evidence to a positive factual claim.

4. Classify the move: an inference whose only support is that the opposite has not been demonstrated is the appeal to ignorance (argumentum ad ignorantiam).

Cross-check — the other named patterns each require a feature this argument does not have.

• Hasty generalization needs premises citing a few observed instances and a conclusion covering the whole class; here not a single instance is sampled.

• Slippery slope needs a claim that one step will set off a chain of further steps ending in an extreme outcome; here no consequence of any step is mentioned.

• Equivocation needs one term used in two different senses across the argument; here "psychic powers" and "exist" keep a single sense throughout.

Result — the fallacy committed is the appeal to ignorance. A useful confirmation is that the same premise can be flipped to yield the opposite conclusion ("nobody has proved that psychic powers do exist, therefore they do not exist"); an argument form that can produce contradictory conclusions from one evidential gap is proving nothing at all.