Nov 26, 2012
LOGICAL FALACY_ Documented by Marsigit
The argument presupposes its conclusion: one of the premises assumes that the conclusion is true. An argument that begs the question should not convince anyone.
In the opposite direction is the fallacy of argument from authority. A classic example of this is the Ipse dixit — "He himself said it" — used through the Middle Ages in reference to Aristotle. A modern use is "celebrity spokepersons" in advertisements: that product is good because your favorite celebrity endorses it.
While an appeal to authority is always a logical fallacy, it can be an appropriate rational argument if, for example, it is an appeal to expert testimony—a type of inductive argument.
By definition, logical fallacies are invalid, but they can often be written or rewritten so that they follow a valid argument form; and in that case, the challenge is to discover the false premise, which makes the argument unsound.