PHIL102: Introduction to Critical Thinking and Logic

In argumentation theory, an argumentum ad populum (Latin for "argument to the people") is a fallacious argument that concludes a proposition must be true because so many, or most, people believe it. "If many believe so, it is so."

We also call this type of argument an appeal to the masses, appeal to belief, appeal to the majority, appeal to democracy, appeal to popularity, argument by consensus, consensus fallacy, authority of the many, bandwagon fallacy, vox populi, argumentum ad numerum ("appeal to the number"), fickle crowd syndrome, and consensus gentium ("agreement of the clans").

These types of appeals are the basis of a number of social phenomena, such as communal reinforcement and the bandwagon effect. The Chinese proverb "three men make a tiger" refers to the same idea.

This fallacy is similar in structure to 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 supposed 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 period of 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. This is often not the case. (This contributes to conformity.)

The argumentum ad populum can be a valid argument in inductive logic; for example, a poll of a sizeable population may find that 100 percent of the respondents prefer a certain brand or product, rather than the other. You could make a cogent, or strong, argument that the next person you consider will also likely prefer that brand (but not always 100 percent since there could be exceptions). The poll is valid evidence of your claim.

However, this article is unsuitable for deductive reasoning. Your research does not prove the brand the majority prefers is superior to the competition in its composition or that everyone prefers that brand to the other.

Evidence

• According to argumentum ad populum you could claim that smoking is a healthy pastime, because millions of people smoke. However, knowing the dangers of smoking, we say that smoking is not a healthy pastime despite the fact that millions of people smoke.
  
  
• Italian society suppressed Galileo Galilei (1564–1642) the Italian astronomer, and other advocates of heliocentrism (the sun is the center of our solar system), despite the scientific evidence that supported heliocentrism rather than geocentrism (the earth is the center of our solar system).

Source: Wikipedia, https://en.wikipedia.org/wiki/Argumentum_ad_populum
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