15 Fallacies of Relevance
Fallacies of Relevance
Informal Fallacies
Assessing the legitimacy of arguments embedded in ordinary language is rather like diagnosing whether a living human being has any broken bones. Only the internal structure matters, but it is difficult to see through the layers of flesh that cover it. Soon we’ll begin to develop methods, like the tools of radiology, that enable us to see the skeletal form of an argument beneath the language that expresses it. But compound fractures are usually evident to the most casual observer, and some logical defects are equally apparent.
The informal fallacies considered here are patterns of reasoning that are obviously incorrect. The fallacies of relevance, for example, clearly fail to provide adequate reason for believing the truth of their conclusions. Although they are often used in attempts to persuade people by non-logical means, only the unwary, the predisposed, and the gullible are apt to be fooled by their illegitimate appeals. Many of them were identified by medieval and renaissance logicians, whose Latin names for them have passed into common use. It’s worthwhile to consider the structure, offer an example, and point out the invalidity of each of them in turn.
Appeal to Force (argumentum ad baculum)
In the appeal to force, someone in a position of power threatens to bring down unfortunate consequences upon anyone who dares to disagree with a proffered proposition. Although it is rarely developed so explicitly, a fallacy of this type might propose:
- If you do not agree with my political opinions, you will receive a grade of F for this course.
- I believe that Herbert Hoover was the greatest President of the United States.
- Therefore, Herbert Hoover was the greatest President of the United States.
It should be clear that even if all of the premises were true, the conclusion could neverthelss be false. Since that is possible, arguments of this form are plainly invalid. While this might be an effective way to get you to agree (or at least to pretend to agree) with my position, it offers no grounds for believing it to be true.
Appeal to Pity (argumentum ad misericordiam)
Turning this on its head, an appeal to pity tries to win acceptance by pointing out the unfortunate consequences that will otherwise fall upon the speaker and others, for whom we would then feel sorry.
- I am a single parent, solely responsible for the financial support of my children.
- If you give me this traffic ticket, I will lose my license and be unable to drive to work.
- If I cannot work, my children and I will become homeless and may starve to death.
- Therefore, you should not give me this traffic ticket.
Again, the conclusion may be false (that is, perhaps I should be given the ticket) even if the premises are all true, so the argument is fallacious.
Appeal to Emotion (argumentum ad populum)
In a more general fashion, the appeal to emotion relies upon emotively charged language to arouse strong feelings th