Appeal to Common Belief. As explained in the section on Statements, claims made in argumentation can be divided into those of verification, evaluation, and advocacy. Surveys of common beliefs and popular opinions are a legitimate way to support some evaluative statements, but they can never be used to argue the accuracy of most statements of verification. Such fallacies are also called appeals to opinion, to belief, and to popular belief. Consider the following claims:

  1. Spitting on the sidewalk is illegal.
  2. Spitting on the sidewalk is disgusting.
Now consider two ways of substantiating each of these claims: looking in a book, and taking a public opinion poll. In the case of legality, which is a claim of verification, we can readily imagine finding conclusive support in the form of a statute in a law book. But even if 100% of the people responding to a poll said spitting was illegal, it might not be, because legality is determined by laws enacted, not people's opinions. In the other case, however, it seems there can be no definitive answer. Whether we look in a book or do a survey, something is disgusting only if you think it so; and if enough people agree with you, then that opinion is generally accepted in your culture or society.

The point is that using popular opinions to support a claim that must be verified in another manner is a fallacious appeal to common belief. Supporting an evaluative statement with factual evidence would be just as fallacious, but much less common. We might call that an appeal to plausible facts.

Exercises

1. Which of the following claims is a fallacious appeal to common belief?

San Jose has a bigger population than San Francisco.

Most people don't know that San Jose has a bigger population than San Francisco.

Most people know that San Jose has a bigger population than San Francisco.

San Jose has a bigger population than San Francisco because most people think so.

1. Which of the following claims is a fallacious appeal to common belief? You answered:

San Jose has a bigger population than San Francisco.

Imagine trying to establish the exact population of any city by asking people individually! Population figures are established by counting residents in a census, which is not the same as an opinion poll because a census surveys the existence of individuals, and not their opinions. This claim happens to be true, but even if it were false, that would not make it into an appeal to belief.

1. Which of the following claims is a fallacious appeal to common belief? You answered:

Most people don't know that San Jose has a bigger population than San Francisco.

This claim has two parts: one is the statement that San Jose has a bigger population, and the other that most people do not know this. Notice that both of these are statements of verification: the population issued can be verified by census results, and what people think about this can be verified by an opinion poll. Therefore, this claim cannot be a fallacious appeal to common belief.

1. Which of the following claims is a fallacious appeal to common belief? You answered:

Most people know that San Jose has a bigger population than San Francisco.

This claim has two parts: one is the statement that San Jose has a bigger population, and the other that most people know this. Notice that both of these are statements of verification: the population issued can be verified by census results, and what people think about this can be verified by an opinion poll. Therefore, this claim cannot be a fallacious appeal to common belief.

1. Which of the following claims is a fallacious appeal to common belief? You answered:

San Jose has a bigger population than San Francisco because most people think so.

Correct!!

A survey could verify whether or not most people think San Jose has the bigger population, but either way, the population of a city cannot be determined by popular opinion, so this is an example of a fallacious appeal to common beliefs.

Congratulations!

You have completed the exercises for fallacious appeal to common belief.