Appeal to authority, or the argument from authority, isn’t inherently a logical fallacy, but
it can quickly turn into one. It’s a form of argument that appeals to an authority on a
subject as a proof that a certain statement is probably true. The authority could be a
person, a study, a book, etc.
John is an authority on aircraft.
John says the first aircraft pre-dated the Wright Brothers.
It is probably true that the first aircraft pre-dated the Wright Brothers.
The American Academy of Pediatrics is an authority on childcare.
The AAP says children are safer in rear-facing car seats.
It is probably true that children are safer in rear-facing car seats.
The appeal to authority becomes a logical fallacy when the appeal is to someone or
that is not an authority in the field, when experts in the field disagree, or when the
authority said something that can’t be taken seriously. For example: she was drunk or joking,
or her statement was taken out of context.
If John, in the first example above, joked that one could define a bird as an aircraft and in that
case aircraft had existed for millions of years, then it would be a logical fallacy to cite him
as saying aircraft had existed for millions of years.
Or, if John is actually just your neighbor who reads books about airplanes instead of a recognized
authority in the field, then you can’t cite him in a serious debate about aircraft. (Perhaps
it would be acceptable in an argument among friends, if John knows more than either of you.)