7: Sharpshooter & Tautology

Informal Fallacies

Key Terms

Modus Ponens
Modus Tollens
Disjunctive Syllogism
Reduction Fallacy
Post Hoc Ergo Propter Hoc
Texas Sharpshooter Fallacy
Tautology

  • Not logical
  • Pseudo-reasoning (false reasoning)
  • Unsound arguments

Fallacies of Cause

  • Deny, confuse, or falsify the cause related to an argument
  • Four types:
    • Reduction fallacy
    • Post hoc ergo propter hoc
    • Texas Sharpshooter fallacy
    • Tautology


Texas Sharpshooter Fallacy

  • Based on a joke about a Texan firing random shots into the side of a barn, then circling the best cluster of holes with a piece of chalk and declaring himself a "sharpshooter," as if he'd been aiming for that particular circle all along
  • Pattern found among pieces of information with no causal relationship

Example

  • Look! I counted every other third letter on this page, then I erased every fifth vowel and it spells out JFK Shot! It must be a prophesy!


Tautology

  • Statement claimed to be true by saying the same thing twice.

Example

  • "A free gift"
  • Our politician will win because he is the better candidate.
  • I like the Dallas Cowboys because they're my favorite team.


Problems with these fallacies

  • Conclusions drawn from insufficient information
  • The Texas Sharpshooter Fallacy assumes causation when in fact there may be no connection
  • The Tautology fails to provide any type of support for the argument