Argumentum ad populum
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 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. 
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.)
The philosopher Irving Copi defined argumentum ad populum ('appeal to the people') differently from an appeal to popular opinion itself, as an attempt to rouse the "emotions and enthusiasms of the multitude".
Valid/Strong and Invalid/Weak uses
The argumentum ad populum can be a cogent (strong) argument in inductive logic. For example, a poll of a sizeable population may find 100% prefer a certain brand of product over another. A cogent argument can then be made that the next person to be considered will also very likely prefer that brand (but not always 100% since there could be exceptions), and the poll is strong evidence of that claim. An example of a weak inductive argument, however, would be saying: "Support the brand of the product. People need a practical product to ensure the fulfillment of its consumers as they say such a product from a particular brand is required according to the polls. People have suffered too long for not receiving the product from this brand." The problem stems from the conclusion likely not following from the premises. What is so special about this product? How is it certain if one product isn't used by the majority, is responsible for their suffering? How will this product lead to a better quality of life? Why is this product made? How can it be induced the polls aren't from a biased sample? These are some of the questions which concern the overall strength of the argument inductively.
For deductive reasoning as proof, for instance, to say the poll proves the preferred brand is superior to the competition in its composition or that everyone prefers that brand to the other.
This section may stray from the topic of the article. (December 2019)
Linguistic descriptivists argue that correct grammar, spelling, and expressions are defined by the language's speakers, especially in languages which do not have a central governing body. According to this viewpoint, if an incorrect expression is commonly used, it becomes correct. In contrast, linguistic prescriptivists believe that incorrect expressions are incorrect regardless of how many people use them.
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In some circumstances, a person may argue that the fact that Y people believe X to be true implies that X is false. This line of thought is closely related to the appeal to spite fallacy given that it invokes a person's contempt for the general populace or something about the general populace to persuade them that most are wrong about X. This ad populum reversal commits the same logical flaw as the original fallacy given that the idea "X is true" is inherently separate from the idea that "Y people believe X": "Y people believe in X as true, purely because Y people believe in it, and not because of any further considerations. Therefore X must be false." While Y people can believe X to be true for fallacious reasons, X might still be true. Their motivations for believing X do not affect whether X is true or false.
Y=most people, a given quantity of people, people of a particular demographic.
X=a statement that can be true or false.
- "Are you going to be a mindless conformist drone drinking milk and water like everyone else, or will you wake up and drink my product?"[a]
- "Everyone likes The Beatles and that probably means that they didn't have nearly as much talent as <Y band>, which didn't sell out."[b]
- "The German people today consists of the Auschwitz generation, with every person in power being guilty in some way. How on earth can we buy the generally held propaganda that the Soviet Union is imperialistic and totalitarian? Clearly, it must not be."[c]
- "Everyone loves <A actor>. <A actor> must be nowhere near as talented as the devoted and serious method actors that aren't so popular like <B actor>."
In general, the reversal usually goes: Most people believe A and B are both true. B is false. Thus, A is false. The similar fallacy of chronological snobbery is not to be confused with the ad populum reversal. Chronological snobbery is the claim that if belief in both X and Y was popularly held in the past and if Y was recently proved to be untrue then X must also be untrue. That line of argument is based on a belief in historical progress and not—like the ad populum reversal is—on whether or not X and/or Y is currently popular.
- See: "MTN DEW is a non-conformist brand that's all about taking life to the next level." PowerPoint Presentation
- These ideas are paraphrased from this presentation by authors Andrew Potter and Joseph Heath in which they state:
- For example, everybody would love to listen to fabulous underground bands that nobody has ever head of before, but not all of us can do this. Once too many people find out about this great band, then they are no longer underground. And so we say that it's sold out or 'mainstream' or even 'co-opted by the system'. What has really happened is simply that too many people have started buying their albums so that listening to them no longer serves as a source of distinction. The real rebels therefore have to go off and find some new band to listen to that nobody else knows about in order to preserve this distinction and their sense of superiority over others.
- These ideas are paraphrased from the 'Baader Meinhof Gang' article at the True Crime Library, which states:
- Gudrun Ensslin may have been wrong about many or most things, she was not speaking foolishly when she spoke of the middle-aged folk of her era as "the Auschwitz generation." Not all of them had been Nazis, of course, but a great many had supported Hitler. Many had been in the Hitler Youth and served in the armed forces, fighting Nazi wars of conquest. A minority had ineffectively resisted Nazism but, as a whole, it was a generation coping with an extraordinary burden of guilt and shame... many of the people who joined what would come to be known as the Baader-Meinhof Gang were motivated by an unconscious desire to prove to themselves that they would have risked their lives to defeat Nazism... West Germans well knew. Many of them had relatives in East Germany and were well aware that life under communism was regimented and puritanical at best and often monstrously oppressive.
- Walton, Douglas N. (1999). Appeal to Popular Opinion. The Pennsylvania State University Press. pp. 61–62. ISBN 0-271-01818-6. LCCN 98031384.CS1 maint: ref=harv (link)
- Conway, David; Munson, Ronald (1997). The Elements of Reasoning (2nd ed.). Wadsworth Publishing Company. pp. 127–128. ISBN 0-534-51672-6.
- Epstein, Richard L.; Rooney, Michael (2017). Critical Thinking (5th ed.). Socorro, N.M.: Advanced Reasoning Forum. p. 76. ISBN 978-1-938421-32-7. LCCN 2017471425.CS1 maint: ref=harv (link)
- Tittle, Peg (2011). Critical Thinking: An Appeal to Reason. Routledge. p. 136. ISBN 978-0-203-84161-7.CS1 maint: ref=harv (link)
- Walton (1999), pp. 81, 85.
- Walton (1999), p. 123.
- Govier, Trudy (2009). A Practical Study of Argument (7th ed.). Cengage Learning. p. 162. ISBN 978-0-495-60340-5.CS1 maint: ref=harv (link)
- Engel, S. Morris (1994). Fallacies and Pitfalls of Language: The Language Trap. New York: Dover Publications. pp. 145–6. ISBN 0-486-28274-0. LCCN 94019770.
- Hinderer, Drew (2005). Building Arguments. Eugene, Ore.: Wipf and Stock Publishers. ISBN 978-1-59752-076-8.
- McCraw, Benjamin W. (2018). "Appeal to the People". In Arp, Robert; Barbone, Steven; Bruce, Michael (eds.). Bad Arguments: 100 of the Most Important Fallacies in Western Philosophy. John Wiley & Sons. pp. 112–114. ISBN 978-1-119-16790-7.
- Van Vleet, Jacob E. (2011). Informal Logical Fallacies: A Brief Guide. University Press of America. p. 20. ISBN 978-0-7618-5432-6. LCCN 2016448028.
- Walton (1999), p. 197.
- Hansen, Hans (May 29, 2015). "Fallacies". Stanford Encyclopedia of Philosophy. Stanford University.
- Rescher, Nicholas; Schagrin, Morton L. "Fallacy". Encyclopædia Britannica. Retrieved December 21, 2019.
- Hitchcock, David (2017). On Reasoning and Argument: Essays in Informal Logic and on Critical Thinking. Springer. p. 406. ISBN 978-3-319-53561-6. LCCN 2017930649.
- Woods, John (2012). "A History of the Fallacies in Western Logic". In Gabbay, D.M.; Pelletier, F.J.; Woods, J. (eds.). Logic: A History of its Central Concepts. Handbook of the History of Logic. North-Holland. p. 561. ISBN 978-0-08-093170-8.CS1 maint: ref=harv (link)
- Walton, Douglas N. (1989). "Appeals to emotion". Informal Logic: A Handbook for Critical Argumentation. Cambridge University Press. p. 84. ISBN 0-521-37032-9. LCCN 88030762.CS1 maint: ref=harv (link)
- Freeman, James B. (1995). "The Appeal to Popularity and Presumption by Common Knowledge". In Hansen, Hans V.; Pinto, Robert C. (eds.). Fallacies: Classical and Contemporary Readings. The Pennsylvania State University Press. p. 266. ISBN 0-271-01416-4.
- Walton, Douglas N. (1992). "Argumentum Ad Populum". The Place of Emotion in Argument. The Pennsylvania State University Press. pp. 66–7. ISBN 0-271-00833-4. LCCN 91030515.CS1 maint: ref=harv (link)
- Walton (1992), p. 65.
- Walton, Douglas N. (1980). "Why Is the 'ad Populum' a Fallacy?" (PDF). Philosophy & Rhetoric. 13 (4): 264–278. ISSN 0031-8213. JSTOR 40237163. Archived (PDF) from the original on March 29, 2016.
- "Argumentum ad Populum (Appeal to Numbers)", ThoughtCo.
- "Bandwagon Fallacy", Excelsior College Online Writing Lab
- "Bandwagon Fallacy" at The Fallacy Files
- "Philosophy 103: Introduction to Logic: Argumentum Ad Populum", Lander University