Logical Fallacies

​Logical fallacies are errors in logic and reasoning that can occur in a writer’s or speaker’s argument. Like rhetorical devices, logical fallacies attempt to persuade the audience. However, unlike rhetorical devices, logical fallacies contain misleading and often false statements.

Also known as Fallacious Reasoning

​Some logical fallacies are so common that they have names. The statement “Only a coward would vote for this, bill” is an example of an ad hominem fallacy. It is a personal attack. Ad hominem is a Latin phrase that means “against a person.” This type of argument is based on faulty reasoning because it simply aims to discredit one’s opponent rather than use logic to disprove the opponent’s claim.

Avoiding logical fallacies improves the strength of a writer or speaker’s rhetoric, or their written or oral argument. When you conduct research, examine sources for logical fallacies in someone else’s rhetoric. It can help you identify when a person’s argument may be misleading.

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Match

Match the following

• logical fallacy

• the art of speaking and writing persuasively

• a writing or speaking technique that helps to make arguments more persuasive

an error in logic and reasoning

rhetoric

rhetorical device

• an error in logic and reasoning

• rhetoric

• rhetorical device

Multiple Choice

Not every school can be as enlightened as LACS, but every school should try. Teachers must either incorporate intrinsic motivation into their classrooms or be left with a system of rewards and punishments that stifles creativity and students’ desire to learn. Teachers’ behaviors may even affect student achievement. A 2014 study that clustered intermediate-level students into three groups—high intrinsic and high extrinsic motivation, high intrinsic and low extrinsic motivation, and low intrinsic and high extrinsic motivation—found that the students who were primarily intrinsically motivated outperformed their fellow students and showed the greatest increase in achievement over the course of a school year.

The argument that teachers must incorporate intrinsic motivation or be left with a rewards and punishment system that stifles students’ desire to learn is a logical fallacy based on—

• an incorrect premise.

• a hasty generalization.

• a faulty piece of evidence.

• an either-or fallacy.

Multiple Choice

Not every school can be as enlightened as LACS, but every school should try. Teachers must either incorporate intrinsic motivation into their classrooms or be left with a system of rewards and punishments that stifles creativity and students’ desire to learn. Teachers’ behaviors may even affect student achievement. A 2014 study that clustered intermediate-level students into three groups—high intrinsic and high extrinsic motivation, high intrinsic and low extrinsic motivation, and low intrinsic and high extrinsic motivation—found that the students who were primarily intrinsically motivated outperformed their fellow students and showed the greatest increase in achievement over the course of a school year.

Analyzing the effect of the author’s use of the logical fallacy in this paragraph allows the reader to—

• correct the author’s errors.

• research evidence about the topic.

• evaluate the effectiveness of the author’s argument.

• become an expert on the issue being discussed.

Multiple Choice

Not every school can be as enlightened as LACS, but every school should try. Teachers must either incorporate intrinsic motivation into their classrooms or be left with a system of rewards and punishments that stifles creativity and students’ desire to learn. Teachers’ behaviors may even affect student achievement. A 2014 study that clustered intermediate-level students into three groups—high intrinsic and high extrinsic motivation, high intrinsic and low extrinsic motivation, and low intrinsic and high extrinsic motivation—found that the students who were primarily intrinsically motivated outperformed their fellow students and showed the greatest increase in achievement over the course of a school year.

What effect does the use of the logical fallacy in this paragraph have on the credibility of the author’s argument?

• It strengthens the argument because it shows that the author carefully researched the results.

• It strengthens the argument because it shows that the author has narrowed the potential conclusions.

• It weakens the argument because it shows that the author may have failed to consider all outcomes.

• It weakens the argument because it shows that the author has based the argument on an incorrect idea.