From Wikipedia, the free encyclopedia.
A logical fallacy is an error of argument; it is a mistake in the way that the propositions (in the argument) are inter-related. When there is a fallacy (i.e. mistake) in the argument, then the argument is said to be invalid. That is, the conclusion does not follow (logically) from the propositions (sentences) advanced to support it. This structural mistake is not the same as the truth or falsity of the statements being made; the conclusion may be true, but it is said to be invalid because it doesn't follow from the arguments (premises) presented.
Arguments intended to persuade may be convincing to many listeners despite containing such fallacies. The truth of the premises may even significantly increase the probability of the truth of the conclusion. But they are nonetheless flawed. Recognizing these fallacies is sometimes difficult.
Here is an example of a fallacious argument. James wants to argue that all killing is wrong, so James argues as follows:
- If one should not do X, all X is wrong. (X can be any action.)
- One should not kill.
- Therefore, all killing is wrong.
Here is another example of a logical fallacy. Suppose Barbara argues like this:
- Andre is a good tennis player.
- Therefore, Andre is good — a morally good person.
Some fallacies are used freely in the media and politics. For example, when one politician says to another, "You don't have moral authority to say X", he is making the argumentum ad hominem or personal attack fallacy — not addressing the argument but attacking the person who made it.
- Arguably, the politician is not even attempting to make an argument, but is instead offering a moral rebuke. Identifying logical fallacies as such can be difficult.
- 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.
An incomplete list of fallacies