Logical Fallacies

These are errors in reasoning that undermine the logic of an argument. They are often persuasive but are logically flawed.

Formal Fallacies

  1. Affirming the Consequent: Assuming that because the consequent is true, the antecedent must also be true.
    • Example: If it rains, the ground will be wet. The ground is wet, so it must have rained.
  2. Denying the Antecedent: Assuming that because the antecedent is false, the consequent must also be false.
    • Example: If it rains, the ground will be wet. It did not rain, so the ground is not wet.

Informal Fallacies

  1. Ad Hominem: Attacking the person making the argument rather than the argument itself.
    • Example: You can’t trust John’s opinion on climate change; he’s not a scientist.
  2. Straw Man: Misrepresenting someone’s argument to make it easier to attack.
    • Example: Person A: We should improve public education. Person B: Person A wants to raise taxes to pay for fancy schools for the rich.
  3. Appeal to Ignorance (Argumentum ad Ignorantiam): Claiming something is true because it has not been proven false.
    • Example: No one can prove that aliens don’t exist, so they must exist.
  4. False Dilemma (False Dichotomy): Presenting two options as the only possibilities when others exist.
    • Example: You’re either with us or against us.
  5. Slippery Slope: Arguing that a small first step will inevitably lead to a chain of related events culminating in some significant impact.
    • Example: If we allow gay marriage, soon people will want to marry animals.
  6. Circular Reasoning (Begging the Question): The argument’s conclusion is assumed in its premise.
    • Example: The Bible is true because it is the word of God, and we know God exists because the Bible says so.
  7. Hasty Generalization: Making a general statement based on a small or unrepresentative sample.
    • Example: My two friends who are doctors are arrogant, so all doctors must be arrogant.
  8. Red Herring: Introducing irrelevant material to the argument to distract and lead away from the point.
    • Example: Why worry about climate change when there are so many homeless people?
  9. Post Hoc Ergo Propter Hoc (False Cause): Assuming that because one event followed another, it was also caused by it.
    • Example: I wore my lucky socks, and we won the game, so the socks caused the win.
  10. Appeal to Authority: Asserting that a claim is true because an authority or expert makes it, without other supporting evidence.
    • Example: A famous actor says this diet is the best, so it must be true.
  11. Bandwagon (Appeal to Popularity): Arguing that something is true or right because it is popular.
    • Example: Everyone is buying this phone, so it must be the best one.
  12. Appeal to Emotion: Using emotional responses rather than valid logic to persuade.
    • Example: Think of the children! We must ban violent video games.
  13. Appeal to Tradition: Arguing that something is right because it has always been done that way.
    • Example: We should keep using typewriters because we’ve always used them.
  14. False Equivalence: Making a comparison between two things that are not truly comparable.
    • Example: Comparing apples and oranges when discussing their health benefits.
  15. Gambler’s Fallacy: Believing that past random events affect the probabilities in future random events.
    • Example: I’ve flipped heads five times in a row, so the next flip must be tails.
  16. Ad Populum (Appeal to Popularity): Claiming a statement is true because many people believe it.
    • Example: Most people believe in ghosts, so they must exist.
  17. Composition/Division Fallacy: Assuming what is true of the part is true for the whole (composition) or what is true of the whole is true for the parts (division).
    • Example (Composition): Each part of this machine is lightweight, so the machine must be lightweight.
    • Example (Division): The team is the best in the league, so each player must be the best in their position.
  18. No True Scotsman: Dismissing counterexamples to a universal claim by redefining the criteria for membership.
    • Example: No true Scotsman puts sugar on his porridge. (Response: My uncle is Scottish and he puts sugar on his porridge.) No true Scotsman would do that.
  19. Equivocation: Using a word with multiple meanings ambiguously to make an argument.
    • Example: The sign said “fine for parking here,” so I parked because it was fine.
  20. Middle Ground: Assuming that the middle position between two extremes is correct because it is in the middle.
    • Example: Person A says vaccines are safe, Person B says vaccines are dangerous, so the truth must be somewhere in between.

Cognitive Biases Related to Fallacies

While not fallacies per se, cognitive biases can influence faulty reasoning:

  1. Confirmation Bias: Favoring information that confirms preexisting beliefs while disregarding contradictory evidence.
  2. Anchoring Bias: Relying too heavily on the first piece of information encountered (the “anchor”) when making decisions.
  3. Availability Heuristic: Overestimating the importance of information that is readily available or recent.
  4. Hindsight Bias: Believing, after an event has occurred, that one could have predicted the outcome.
  5. Self-Serving Bias: Attributing positive events to oneself and negative events to external factors.

Understanding and identifying these logical fallacies can help improve critical thinking skills and the quality of arguments.

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