Quiz on Formal and Informal Fallacies

What is the main difference between a formal and an informal fallacy?

• Formal fallacies involve incorrect grammar, while informal fallacies involve incorrect facts.

• Formal fallacies are errors in the logical structure, while informal fallacies are errors in the connection between argument and evidence.

• Formal fallacies involve incorrect use of language, while informal fallacies involve mathematical errors.

• Formal fallacies only happen in math, while informal fallacies only happen in literature.

Which of the following is an example of a formal fallacy?

• "I saw a black cat before my test, and I failed. Black cats bring bad luck."

• "All cats are animals. A dog is an animal. Therefore, a dog is a cat."

• "The mayor has a beard. Bearded people are untrustworthy. Therefore, the mayor cannot be trusted."

• "That student looks smart, so he must be the best in class."

Informal fallacies are often caused by:

• Incorrect word order

• Faulty use of language or irrelevant information

• Mathematical errors

• Lack of punctuation

Which of the following statements contains an informal fallacy?

• "All roses are flowers. Some flowers fade quickly. Therefore, all roses fade quickly."

• "I have never seen a penguin fly. Therefore, penguins cannot fly."

• "Our leader must be honest because he looks like an honest person."

• "If A = B and B = C, then A = C."

Why is the statement "Katrina can’t represent our class in the singing contest. Her beauty is not alluring enough to win." an informal fallacy?

• It assumes beauty is related to singing ability.

• It follows a proper logical structure.

• It is mathematically incorrect.

• It contains a grammar mistake.

If I meet James’s girlfriend, that proves he has one. I have not met her, so James must not have a girlfriend.

• Formal Fallacy

• Informal Fallacy

Andrew, my classmate, is a miscreant. He just has a face that I cannot trust, so he must be a troublemaker.

• Formal Fallacy

• Informal Fallacy

All birds have wings. Penguins have wings. Therefore, penguins can fly.

• Formal Fallacy

• Informal Fallacy

That politician wears glasses, so he must be intelligent.

• Formal Fallacy

• Informal Fallacy

Some mammals are carnivores. A dog is a mammal. Therefore, a dog must be a carnivore.

• Formal Fallacy

• Informal Fallacy