The Bandwagon Fallacy

The bandwagon fallacy — also called argumentum ad populum, appeal to the people, or appeal to popularity — occurs when someone argues that a claim is true or correct because many people believe it. The structure is: “A lot of people think X. Therefore X is true.”

This is fallacious because the popularity of a belief is, in most cases, independent of its truth. Many widely held beliefs turn out to be false. Many true claims have been historically minority positions. The number of adherents tracks social, cultural, and historical factors that have little to do with whether the underlying claim is correct.

Historical examples

It used to be widely believed that the earth was the center of the universe. The belief was nearly universal among educated people for most of recorded history. It was also wrong. The popularity did no work to make it true.

Closer to home: many beliefs that were widely held in 1950 are no longer held today. Many beliefs widely held today will not be held in 2100. The shifting majority does not track shifting truth. It tracks shifting cultural conditions.

When it sounds reasonable

The bandwagon fallacy is particularly seductive because there are cases where popularity does carry some evidential weight. If most experts in a field believe X, that’s relevant information — though, as we discussed in the appeal to authority post, it’s not by itself decisive.

Similarly, if most people who have tried a product report it works, that’s relevant information for someone considering the product. The aggregate experience of many users has some predictive value.

These cases are not quite the bandwagon fallacy. The bandwagon fallacy specifically involves the inference from belief to truth, not from experience to prediction. The distinction is subtle but important.

How marketers use it

Advertising relies heavily on the bandwagon fallacy. “Eight out of ten dentists recommend this toothpaste.” “Join the millions who have switched to…” The implicit argument is that you should make the same choice because many others have.

These claims sometimes contain legitimate information (the dentists really do recommend the toothpaste; the millions really did switch). But they are doing rhetorical work that the underlying information does not warrant. The fact that many people use a product tells you something about the product’s market position. It tells you much less about whether the product is good for you, specifically.

How to push back

When you encounter a bandwagon argument, the most useful question is: why do many people believe this? Sometimes the answer is “because it’s true, and they figured it out.” Often the answer is “because they were taught to,” or “because believing it is convenient,” or “because the alternative requires uncomfortable revision of other beliefs.”

These are not equivalent reasons. Distinguishing between them is the work of critical thinking. Popularity is a starting point for that work, not a substitute for it.