A fallacy of authority is a type of logical fallacy in which the authority of a person is taken as evidence that any statement he or she makes is true. This type of fallacy is often committed by someone who uses a statement made by someone else as evidence of a particular position on a subject. The area of expertise for that authority, however, may never be called into question and so the person may not truly be an authority in a relevant field. A fallacy of authority can also occur simply due to the fact that someone’s position as an authority in a subject does not make him or her infallible.
Also called an appeal to authority, a fallacy of authority is typically committed when someone uses a statement made by someone else as proof of a particular position. While this in and of itself is not grounds for a fallacy to have been committed, the authority of the person should be called into question. For example, just because someone is a successful business person who has made a great deal of money does not inherently mean that he or she can be a successful politician. This type of fallacy of authority is often committed when people associate success or knowledge in one field as being emblematic of overall success or knowledge in all fields.
A fallacy of authority can also occur when someone claims to be an authority on a particular subject, in which no reasonable authorities can truly exist. For example, if someone makes a claim, as an authority, about life on other planets, then this type of fallacy has likely been committed. Even an expert in the field of astronomy and the study of other worlds cannot be considered an authority on life on other worlds. This is simply due to limitations of human experience in this particular subject area, and any statements made by that person should be considered on their own merit and not by the authority of the speaker.
Anyone arguing for or against a particular point should also keep in mind that a fallacy of authority can also be committed unwittingly. Someone can be an authority in a relevant field, and still make a statement that is incorrect or untrue. Just because someone is an expert in mathematics, for example, does not mean that he or she could not be wrong about some aspect of math. To avoid a fallacy of authority, the message, rather than the messenger, should be considered and evaluated for validity.