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Argument From Ignorance

October 30th, 2009

Taxonomy – Where am I?

Argument From Ignorance (ad ignorantiam)

classification : informal – fallacies of defective induction

A logical fallacy of irrelevance occurring when one claims that something is true only because it hasn’t been proved false, or vice versa.


A claims truth or falsity depends upon supporting or refuting evidence to the claim in favor of an alternative view. Not knowing that a statement is true is taken to be proof that it is false.


Jim said he is smarter than David but failed to prove it. Therefore his argument ( assertion ) is logically flawed. Claiming something does not make it true.

Failing to prove that Unicorns do not exist, affirms that they do exist

If such actions were not illegal, then they would not be prohibited by the law.

Other Names:

lack-of-knowledge inference

negative evidence

default reasoning

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Categories: Logic