The first common fallacy canvassed in our book Humbug! is Appeal to Authority. Our short definition of appeal to authority is as follows: "The advocate makes an unwarranted appeal to an authoritative person or organization in support of a proposition". Unwarranted in this context means that the appeal is without foundation, and that the supposed "authority" does not really lend any weight to the advocate's proposition (because the authority of the authority on this particular matter is not convincing, or because the advocate is falsely claiming that the authority would agree with the advocate's position).
There is a subspecies of appeal to authority which is much more bizarre than a commonplace appeal to authority. This subspecies of appeal to authority is worthy of comment here because it is increasingly common, and often passes unnoticed by those who should know better. It is Appeal to Celebrity.
Consider the commonplace case. The celebrity is appearing on a chat show, or a news and current affairs program. The celebrity is perhaps an actor, a model, a sportsperson, a "reality television" contestant, or a Greens senator. Whatever the claim to fame, the celebrity is not known for deep thinking. And yet... the interviewer inevitably asks the celebrity about his or her profound thoughts on some deep and complex issue – multilateral defence treaties, bilateral trade agreements, reform of the United Nations, health funding, dry land salinity etc etc etc. And the celebrity is eager to pontificate at length on any of these, and presumably the more impressionable viewers will be swayed by the celebrity's half-baked opinions, just because the celebrity is a celebrity.
Just once I'd like to see a journalist-interviewer practice real journalism and say: "sorry to interrupt you there Sean, but you're talking about politics now, and we're not interested; after all, you're only an actor".