In argumentation theory, an argumentum ad populum (Latin for “appeal to the people”) is a fallacious argument that concludes that a proposition must be true because many or most people believe it, often concisely encapsulated as: “If many believe so, it is so”.
Other names for the fallacy include common belief fallacy or appeal to (common) belief, appeal to the majority, appeal to the masses, appeal to popularity, argument from consensus, authority of the many, bandwagon fallacy, consensus gentium (Latin for “agreement of the people”), democratic fallacy, and mob appeal.
Argumentum ad populum is a type of informal fallacy, specifically a fallacy of relevance, and is similar to an argument from authority (argumentum ad verecundiam). It uses an appeal to the beliefs, tastes, or values of a group of people, stating that because a certain opinion or attitude is held by a majority, it is therefore correct.
Appeals to popularity are common in commercial advertising that portrays products as desirable because they are used by many people or associated with popular sentiments instead of communicating the merits of the products themselves.
The inverse argument, that something that is unpopular must be flawed, is also a form of this fallacy.
The fallacy is similar in structure to certain other fallacies that involve a confusion between the justification of a belief and its widespread acceptance by a given group of people. When an argument uses the appeal to the beliefs of a group of experts, it takes on the form of an appeal to authority; if the appeal is to the beliefs of a group of respected elders or the members of one’s community over a long time, then it takes on the form of an appeal to tradition. It is also the basis of a number of social phenomena, including communal reinforcement and the bandwagon effect. The Chinese proverb “three men make a tiger” concerns the same idea.
One who commits this fallacy may assume that individuals commonly analyze and edit their beliefs and behaviors based on majority opinion. This is often not the case. (See conformity.)
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