appeal to authority (thing)

A logical fallacy where an authority is cited in support of the argument. An Appeal to Authority is invalid when

• The person is not an expert in the particular field
• There is widespread disagreement among experts in the field
• The expert was drunk, joking, etc.

Also, be wary when you hear the expert's testimony through second-hand sources. hearsay is usually inaccurate.

Example: The one given in Blackavar's writeup in ad vericundiam. Bill Clinton isn't a cigar expert.
Example: "J. Random Psychologist says recovered memories are always fake." Many psychologists disagree on this topic.
Example: "Linux is a movement to overthrow the government! Linus Torvalds said he plans on world domination"

To prove the fallacy, show that one of the bullet points above applies.