Ad populum

Ad populum, Latin for "to the populous", is a fallacy in which an ideas popularity or general use is used as an example of its validity. This can also be called the Bandwagon or Herd Mentality fallacy.

This fallacy is one of the more common fallacies, as it's used in every day advertising to sell products.

What makes this is a logical fallacy is that just because something is widely adopted does not mean it is the only, correct, or best option, as people as a group can be wrong and are easily motivated by trends, rather than facts or logic.

The ad populum fallacy is also used to make objective statements about subjective facts, with the popularity being used as evidence.

An example of the Ad populum fallacy would be someone saying that because Facebook is widely used, that it is automatically good.