Argument from authority (also known as appeal to authority) is a fallacy of defective induction, where it is argued that a statement is correct because the statement is made by a person or source that is commonly regarded as authoritative. The most general structure of this argument is:
This is a fallacy because the truth or falsity of a claim is not related to the authority of the claimant, and because the premises can be true, and the conclusion false (an authoritative claim can turn out to be false). It is also known as argumentum ad verecundiam (Latin: argument to respect) or ipse dixit (Latin: he himself said it).
On the other hand, arguments from authority are an important part of informal logic. Since we cannot have expert knowledge of many subjects, we often rely on the judgments of those who do. There is no fallacy involved in simply arguing that the assertion made by an authority is true. The fallacy only arises when it is claimed or implied that the authority is infallible in principle and can hence be exempted from criticism.
Origin of the expression
The Latin word verecundia means modesty or shyness, and argumentum ad vercundiam means literally 'argument towards modesty', though the phrase is normally rendered in English as Argument from Authority.
The expression was invented by John Locke, who explained the meaning of the term as follows: "When men are established in any kind of dignity, it is thought a breach of 'modesty' for others to derogate any way from it, and question the authority of men who are in possession of it."
There are two basic forms of appeal to authority, based on the authority being trusted. The more relevant the expertise of an authority, the more compelling the argument. Nonetheless, authority is never absolute, so all appeals to authority which assert that the authority is necessarily infallible are fallacious. (See infallibility, Divine authority, Argument from ignorance, prejudice, and poisoning the well.)
The first form of the appeal to authority is when a source presenting a position on a subject mentions some authority who also holds that position, but who is not actually an authority in that area. For instance, the statement "Arthur C. Clarke released a report showing it is necessary to floss three times daily" should not convince many people of anything about flossing, as Clarke, a science fiction writer, was not a known expert on dental care. Much advertising relies on this logical fallacy in the form of endorsements and sponsorships. A sportsperson or actor, for example, is no more likely than average to have any special knowledge of watches or perfume, but their endorsement of a particular brand of watch or perfume is very valuable in advertising terms. Alternatively they may not be experts in the relevant part of the field (for example, an expert in litigation may not be an expert on trust law or commercial law even though they are indeed a civil lawyer). In some cases, the advertisers use an actor's well-known role to imply that the person has authority in an area; an actor who plays a doctor on television may appear in their white coat, and endorse a drug or health product.
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