An error in reasoning that renders an argument invalid.
Common Types of Logical Fallacies:
Ad Hominem, Ad Misericordiam, Amphiboly, Appeal to Authority, Appeal to Force, Appeal to Humor, Appeal to Ignorance, Appeal to the People, Bandwagon, Begging the Question, Circular Argument, Complex Question, Contradictory Premises, Dicto Simpliciter, Equivocation, Etymological Fallacy, False Analogy, False Dilemma, Gambler's Fallacy, Hasty Generalization, Misleading Vividness, Name-Calling, Non Sequitur, Paralepsis, Poisoning the Well, Post Hoc, Red Herring, Slippery Slope, Stacking the Deck, Straw Man, Tu Quoque, Undistributed Middle
- Reasons to Avoid Logical Fallacies in Your Writing
"There are three good reasons to avoid logical fallacies in your writing. First, logical fallacies are wrong and, simply put, dishonest if you use them knowingly. Second, they take away from the strength of your argument. Finally, the use of logical fallacies can make your readers feel that you do not consider them to be very intelligent."
(William R. Smalzer, Write to Be Read: Reading, Reflection, and Writing, 2nd ed. Cambridge Univ. Press, 2005)
- Informal Fallacies
"Although some arguments are so blatantly fallacious that at most they can be used to amuse us, many are more subtle and can be difficulty to recognize. A conclusion often appears to follow logically and nontrivially from true premises, and only careful examination can reveal the fallaciousness of the argument.
"Such deceptively fallacious arguments, which can be recognized as such with little or no reliance on the methods of formal logic, are known as informal fallacies."
(R. Baum, Logic. Harcourt, 1996)
- Formal and Informal Fallacies
"There are two main categories of logical errors: formal fallacies and informal fallacies.
"The term 'formal' refers to the structure of an argument and the branch of logic that is most concerned with structure--deductive reasoning. All formal fallacies are errors in deductive reasoning that render an argument invalid. The term 'informal' refers to the non-structural aspects of arguments, usually emphasized in inductive reasoning. Most informal fallacies are errors of induction, but some of these fallacies can apply to deductive arguments as well."
(Magedah Shabo, Rhetoric, Logic, and Argumentation: A Guide for Student Writers. Prestwick House, 2010)
- Example of a Logical Fallacy
"The arguments in support of civic education are often seductive. . . .
"Although we might emphasize different civic virtues, don't we all honor a love for our country [and] a respect for human rights and the rule of law . . .? Since no one is born with an innate understanding of these virtues, they must be learned, and schools are our most visible institutions for learning.
"But this argument suffers from a logical fallacy: Just because civic virtues must be learned, does not mean they can be easily taught--and still less that they can be taught in schools. Nearly every political scientist who studies how people acquire knowledge and ideas about good citizenship agrees that schools and, in particular, civics courses have no significant effect on civic attitudes and very little, if any, effect on civic knowledge."
(J. B. Murphy, New York Times, Sep. 15, 2002)