Stephen's Guide to the Logical Fallacies

How to Use This Guide


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  • All Fallacies
  • The Fallacies

  • False Dilemma
  • Argument From Ignorance
  • Slippery Slope
  • Complex Question
  • Appeal to Force
  • Appeal to Pity
  • Appeal to Consequences
  • Prejudicial Language
  • Appeal to Popularity
  • Anonymous Authorities
  • Coincidental Correlation
  • Attacking the Person
  • Appeal to Authority
  • Converse Accident
  • Style Over Substance
  • Unrepresentative Sample
  • Hasty Generalization
  • False Analogy
  • Slothful Induction
  • Fallacy of Exclusion
  • Accident
  • Joint Effect
  • Genuine but Insignificant Cause
  • Wrong Direction
  • Complex Cause
  • Begging the Question
  • Irrelevant Conclusion
  • Straw Man
  • Equivocation
  • Amphiboly
  • Accent
  • Composition
  • Division
  • Affirming the Consequent
  • Denying the Antecedent
  • Inconsistency
  • Fallacy of Four Terms
  • Undistributed Middle
  • Illicit Major
  • Illicit Minor
  • Fallacy of Exclusive Premises
  • Drawing an Affirmative Conclusion From a Negative Premise
  • Existential Fallacy
  • Subverted Support
  • Non-Support
  • Untestability
  • Limited Scope
  • Limited Depth
  • Too Broad
  • Too Narrow
  • How to Use This Guide

    Each fallacy is described in the following format:

    Name: this is the generally accepted name of the fallacy
    Definition: the fallacy is defined
    Examples: examples of the fallacy are given
    Proof: the steps needed to prove that the fallacy is committed

    The fallacies are themselves grouped into categories of four to six fallacies each. This grouping is somewhat arbitrary and is for the sake of convenience only.

    Learning About the Fallacies

    The best way to learn about logical fallacies is simply to start at the first page and begin reading. After reading each page, click on the next button. In addition to the definitions of the fallacies themselves, you will be able to read background information, examples, and discussion of the various fallacies.

    After you feel you have mastered the definition of a fallacy, test your knowledge by locating an example and submitting it to this site. All submissions are reviewed, and if your example is a good example, it will be added to the list of examples for that particular fallacy.

    Finally, join in on the discussions. There is a discussion thread for each fallacy as well as more general discussion areas (if you don't like the selection, start your own discussion thread).

    Using Your Knowledge

    In your day-to-day life you will encounter many examples of fallacious reasoning. And it's fun - and sometimes even useful - to point to an argument and say, "A ha! That argument commits the fallacy of false dilemma."

    It may be fun, but it is not very useful. Nor is it very enlightened.

    The names of the fallacies are for identification purposes only. They are not supposed to be flung around like argumentative broadswords. It is not sufficient to state that an opponent has committed such-and-such a fallacy. And it is not very polite.

    This Guide is intended to help you in your own thinking, not to help you demolish someone else's argument. When you are establishing your own ideas and beliefs, evaluate them in the light of the fallacies described here.

    When evaluating the ideas and arguments proposed to you by others, keep in mind that you need to prove that the others' reasoning is fallacious. That is why there is a 'proof' section in the description of each fallacy. The 'proof' section is intended to give you a mechanism for showing that the reasoning is flawed. Apply the methodology described in the 'proof' section to the passage in question. Construct your own argument. Use this argument - not the name of the fallacy - to respond.

    Logic and Truth

    Finally - a point about logic and truth.

    The idea of logic is truth preservation. What that means is that if you start with true beliefs, your reasoning will not lead you to false conclusions.

    But logic does not generate true beliefs. There's no easy way to do that.

    Most people use the evidence of their senses to generate true beliefs. They see that apples grow on trees, that some bananas are yellow, and so on.

    For many other truths, we must rely on faith. That God exists, that right is better than wrong, that truth is a virtue: these are beliefs which cannot be confirmed by the senses, and reflect therefore a certain world view.

    When it comes to conflicts between such basic precepts, logic fails. It is not possible to show that one world view is right and the other is wrong. If a person believes in God, for example, logic is unlikely to change that person's mind, for that belief is ultimately based on faith.

    And remember - most people have non-logical reasons for believing the things they do. They may have political opinions because their parents had them, they may have on-the-job views because they're afraid of being fired, they may think a movie is good because all their friends do.

    These too count as parts of a person's world view. There is no reason for you to hold these beliefs, because you are not subject to the same non-logical factors. But you should be aware that mere reason will not be enough to get them to change their minds.

    So use reason with caution, and if you really want to persuade someone of something, remember that compassion, honesty and tact are as important as logic.

    Enjoy the Guide.

    Created by Stephen Downes, Copyright 2024 CC By-NC-SA