PhilosophyLesson 3 of 3 in the course Logic and Reasoning

Informal Fallacies: Categories, Types, and Analysis

5 flashcards · 5 quiz questions · 5 match pairs · 5 fill-in sentences · English

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Summary

Informal fallacies are reasoning errors that arise not primarily from an argument’s logical form, but from the relationship between its premises and conclusion. This lesson introduces the four broad categories used to recognize these errors.

A formal fallacy is an error in an argument’s structure: even if the premises were true, the form would not guarantee the conclusion. An informal fallacy instead involves the content, relevance, or adequacy of the reasons offered. To assess an informal argument, we often need background knowledge about the world.

All flashcards

What is an informal fallacy?
A reasoning error involving the content, relevance, or strength of an argument’s support, rather than solely its logical form.
What is a formal fallacy?
An error in an argument’s logical structure, such that the form does not properly support the conclusion.
What are the four general categories of informal fallacies?
Fallacies of relevance, weak induction, unwarranted assumption, and diversion.
How does a fallacy of weak induction fail?
Its premises may be relevant, but the evidence is too weak, incomplete, or biased to firmly establish the conclusion.
Does a fallacious argument necessarily have a false conclusion?
No. The conclusion may be true, but the reasons offered do not adequately establish it.

Quiz questions

  1. Someone tries to judge an entire restaurant from two meals there. Which error best describes this reasoning?Answer: A broad conclusion drawn from too few observations.
  2. A person notices that two events occur together and concludes that one caused the other. What is the main error?Answer: Inferring causation from correlation without adequate evidence.
  3. An argument claims that people must either support a proposal or oppose progress, without considering other positions. What fallacy does this illustrate?Answer: A false dichotomy that presents limited options as exhaustive.
  4. A debater claims an opponent wants to end all immigration when the opponent argued only for following existing legal procedures. What fallacy is this?Answer: A strawman that distorts the opponent’s stated position.
  5. An argument uses a premise that simply assumes the disputed conclusion it is meant to establish. What fallacy does it commit?Answer: Begging the question through an unsupported assumption.

Based on Introduction to Philosophy by Nathan Smith (OpenStax), licensed CC BY 4.0. Adapted into a summary, flashcards and quizzes.

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