Appeal to authority

An appeal to authority is a type of argument in logic also known as argument from authority, argumentum ad verecundiam (Latin: argument to respect) or ipse dixit (Latin: he himself said it, where an unsupported assertion depends on the asserter's credibility). It is one method of obtaining propositional knowledge and is a logical fallacy because its method of inference is not rock-solid. On the other hand, there is no fallacy involved in simply arguing that the assertion of the authority is likely to be true.

Forms
There are two basic forms of appeal to authority, based on the authority being trusted. The more relevant expertise of an authority, the more compelling the argument. Nonetheless, authority is never absolute, so all appeals to authority which assert the authorities' claims are definitely true are fallacious.

The first form of the appeal to authority is when a person 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 recently released a report showing it is necessary to floss three times daily" should not convince many people of anything about flossing, as Arthur C. Clarke is not a known expert on dental hygiene. Much advertising relies on this logical fallacy in the form of endorsements and sponsorships.

The second form, citing a person who actually is an authority in the relevant field, carries more weight in that the authority is more likely to be correct. However the possibility of mistake remains.

Appeal to authority as logical fallacy
A (fallacious) appeal to authority argument has the basic form:

The first statement is called a 'factual claim' and is the pivot point of much debate. The last statement is referred to as an 'inferential claim' and represents the reasoning process. There are two types of inferential claim, explicit and implicit. Arguments that (fallaciously) rely on the objectionable aspects of the person for the truth of the conclusion are discussed under ad hominem.
 * 1) A makes claim B;
 * 2) there is something positive about A,
 * 3) therefore claim B is true.

An appeal to authority is a logical fallacy: authorities can be wrong, both in their own field and in other fields; therefore referencing authority does not automatically imply truth. However, referencing authority may carry a high enough probability of truth that it would be correct to base decisions on it.

Examples of appeals to authority

 * Referring to the philosophical beliefs of Aristotle. "If Aristotle said it was so, it is so".
 * Quotes from religious books such as the Bible. "The Bible says X, therefore X is the right thing".
 * Claiming that some crime is morally wrong because it is illegal. "It's against the law for stores to be open on weekends, therefore it's wrong for them to do so". Here the lawmakers are the "authority", whose judgment is taken as correct without debate.
 * Referencing scientific research published in a peer-reviewed journal. "Science (in the form of an article in a prestigious journal) says X, therefore X is so".
 * Believing what one is told by one's teacher. "My teacher said so, therefore it must be right."
 * Something must be true because it is in the news.
 * Something must be true because it is in a textbook.
 * Something must be true because it is in an encyclopedia.
 * Something must be true because it is in Wikipedia.

Discussion
In the Middle Ages, roughly from the 12th century to the 15th century, the philosophy of Aristotle became firmly established dogma, and using the beliefs of Aristotle was an important part of many debates. Aristotle's thought became so central to the philosophy of the late Middle Ages that he became known in Latin as Ille Philosophus, "the philosopher," and quotations from Aristotle became known as ipse dixits ("He, himself, has spoken."). In this case, Aristotle is an example of someone who is an authority in philosophy, but philosophy is an area where direct evidence is less readily available, and therefore, Aristotle's ideas carry weight, but are not the final word. On the other hand, arguing that all astronomers believe that the planet Neptune exists - and therefore, that serves as evidence of the planet's existence - is a more compelling argument because astronomers are knowledgeable in the relevant field and are in a position to readily prove or disprove the existence of the planet (direct experience). However, it is still better to argue from evidence than from what astronomers believe.

Authoritarian ethics is the meta-ethical theory by which one attains ethical knowledge from an authority, for example from a God or from the law (see Divine command theory). The bandwagon fallacy can be viewed as a special case of an appeal to authority, where the authority is public opinion.

A corollary to this is the infamous 'Because I said so' argument much stated by parents and loathed by children. It is a logical fallacy of this kind, in the fact that the parent is an authority figure and, therefore, should have the proper knowledge to make their statements true. However, like most fallacies of this kind, the validity of their statements is only in the form of their individual beliefs, and when pressed for a logical explanation for the reasoning behind their statement, are unable to do so in a satisfactory manner. As such, the basic overall fallacy here is that, as they are the authority figures over a child, the child is supposed to believe that only their parents' statement is explanation enough for it to be so.

Conditions for a legitimate argument from authority
Any argument should ideally be based solely on direct evidence and the argument itself, not on the authority of the messenger drawing the conclusion from the evidence. However, it is rarely possible in common discourse to provide all the direct evidence, so an "appeal to authority" is often used as a shortcut:


 * The authority must have competence in an area, not just glamour, prestige, rank or popularity. A sports or entertainment figure making claims about foreign policy is an example of how this rule is frequently violated.
 * The judgment must be within the authority's field of competence. Linus Pauling won a Nobel Prize for chemistry, then later made claims that massive quantities of vitamin C would prevent cancer in humans.  This claim was in the field of medicine and thus outside his field of competence.
 * The authority must be interpreted correctly. This is particularly a problem in religion; where the Koran, Bible, Torah, etc., have been interpreted with varying and sometimes contradictory results.
 * Direct evidence must be available, at least in principle.
 * The expert should be reasonably unbiased (not unduly influenced by other factors, such as money, political considerations, or religious beliefs). This is why appealing to one's own authority is always illegitimate. The Pope claiming that the Sun revolved around the Earth was an example of an authority making a false claim biased by their religious beliefs.
 * The judgment must be representative of expert opinions on the issue (as opposed to an unrepresentative sample). Lawyers sometimes find a non-representative "expert" to offer a theory which is not generally accepted (such as a so-called Twinkie defense) in hopes of winning their case.
 * A technique is needed to adjudicate disagreements among equally qualified authorities. If scientific testing of the claim is not possible, then the majority of expert opinions is sometimes used to develop a consensus.

Taxonomy
The appeal to authority is a genetic fallacy.