It's been a while since we had a Fallacy Friday, so let's start this Friday off with the argument from authority, or as they say in the Latin: argumentum ad verecundiam.
Respec Mah Authoritah!
Often times when arguing about something that can't be answered by observation or calculation, one might feel the need to appeal to an authority. This authority may or may not even be an expert in the field of that of the argument. A good example of this is when people quote Einstein's opinions about politics as though he were a political philosopher rather than a physicist.
At least in some forms of debate, quoting various sources to support one's position is not just acceptable but often mandatory. But one should only rely on authorities whose expertise relates to the question at hand, especially with regard to questions of fact. Saying, "Albert Einstein believed in God....are you saying that Einstein was wrong?" is committing a fallacy. It doesn't matter what Einstein said about God, politics, or anything else. He's a expert in the realm of physics.
Lemme Do It...I'm The Expert
It's necessary to distinguish between an authority and an expert. If a famous astronomer says that the universe is expanding, then it is very likely that the universe really is expanding. If a qualified doctor says that a patient is suffering from Parkinson's disease, that's most likely the case. In these examples, the astronomer and the doctor are experts in a field, and are addressing topics within their area of expertise. As experts, they have studied their respective fields, are familiar with the state of the art, have studied how to recognize certain events, features or conditions, know how to recognize many problems that might lead a layman astray and how to work around them, and so forth. When we take an expert's word for something, we are saying in effect that if we had the time to learn as much about the field as the expert has, we would be able to examine the evidence and reach the same conclusion.
On the other hand, if the Pope says, ex cathedra, that contraception is a sin, then that's true as well. In this case, the Pope is an authority in matters of sin: it is his job to determine what is and isn't a sin in the Catholic church. In a very real sense, contraception is a sin not because it is intrinsically bad, or even because it contradicts the Bible in some way, or even that "sin" is a real concept, but merely because the Pope has declared it to be so.
Well, You Know What They Say...
In science, there are experts but no authorities. Again, saying that a qualified physicist thinks the universe is expanding is fine, but saying that the President thinks that stem-cell research is of the devil is not. It's only a fallacy if it relies on an unqualified source for information about facts without other qualified sources of verification, or if it implies that some policy must be right simply because so-and-so thought so.