Appeal to tradition

"This is right because we've always done it this way." The appeal to tradition is a very common logical fallacy in which someone proclaims his or her accuracy by noting that "this is how it's always been done."

The assumption behind this argument is that whatever reason was used to come to the old methods of thinking is still valid today; often, this is a false assumption to make.

Humans are creatures of habit; this is the likely cause of the popularity (and, unfortunately, the success) of this argument.

Examples:

"It's always been done that way. We've never done it like that."

"You're crazy! Nobody ever thought like that before!"

"This precedent was set 100 years ago and has been followed many times."

The opposite is the appeal to novelty, claiming something is good because it's new.