The appeal to authority fallacy is associated with attributing truth to a statement based on the authority of the speaker or on the authority of someone who supports the statement. This is fallacious because it assumes truth to be a function of power or prestige rather than objectivity. An authority, simply by being authority, cannot will truth into existence. Insofar as truth exists as an objective reality, it isn’t subject to anyone’s commands.
There are exceptions. For instance, we tend to rely on dictionaries and English usage guides as sources of truth about the English language. But this is not because they reflect any objective truth (as language is a system of agreed upon symbols), but rather because we trust them to reflect truths about how people use the language.
Why do people commit the appeal to authority fallacy?
When someone is a recognized authority on a subject or is otherwise powerful or influential, we hesitate to question that person’s statements. Even if we sense that person may be wrong about something, we assume she has considered the matter carefully in light of her expertise and has come to a surprising conclusion. In the face of this, we’re more likely to doubt our own contrary judgments or to simply allow that person to be a maker of truth.
But of course, the fallacy is not always so complicated. Sometimes an appeal to authority is simply a crutch to prop up a poorly thought out argument.
The key to healthy soil is organic matter. Every gardening guide says so, so it must be true. [Santa Barbara Independent]
It may be true that organic matter makes healthy soil, but the fact that gardening guides say so does not make it true. To make a convincing argument, this writer needs to provide at least a little information about what makes organic matter so beneficial.
Here’s a counterexample:
A pawn on its fifth rank may capture an enemy pawn on an adjacent file that has moved two squares in a single move, as if the pawn had moved only one square. [chess rule via Wikipedia]
As the rules of chess are governed solely by the governing body of the game and have no objective reality apart from these arbitrary rules, it is not an appeal to authority to bring up what the rules say. The authority here is the only source of truth, and accordingly is valid to be argued from.