Formal Fallacies-Appeal to Probability, Bad Reasons, Masked Man & Non Sequitur for Competitive Exams

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Formal Fallacies - Appeal to Probability, Bad Reasons, Masked Man & Non Sequitur

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Fallacies – Formal / Informal

  • Fallacies are errors or tricks of reasoning. We call a fallacy an error of reasoning if it occurs accidentally; we call it a trick of reasoning if a speaker or writer uses it in order to deceive or manipulate his audience

  • Most formal fallacies are errors of logic: the conclusion doesn’t really “follow from” (is not supported by) the premises. Either the premises are untrue or the argument is invalid. Below is an example of an invalid deductive argument.

  • Premise: All black bears are omnivores.

  • Premise: All raccoons are omnivores.

  • Conclusion: All raccoons are black bears.

  • Informal fallacies involve bringing irrelevant information into an argument or they are based on assumptions that, when examined, prove to be incorrect. Formal fallacies are created when the relationship between premises and conclusion does not hold up or when premises are unsound; informal fallacies are more dependent on misuse of language and of evidence.

  • In fallacies of relevance, the premises of the argument are simply not relevant to the conclusion

  • In fallacies of defective induction, premises of the argument, although relevant to the conclusion are so weak and ineffective that relying on them is a blunder

  • In fallacies of presumption, too much is assumed in the premises.

  • In fallacies of ambiguity - Some word or phrase in one part of the argument has a meaning different from that same word or phrase in another part of the argument.

Ethos, Logos & Pathos

  • Ethos is an argument that appeals to ethics, authority, and/or credibility – attack credibility

  • Logos is an argument that appeals to logic - unfair advantage to the claims of the speaker

  • Pathos is an argument that appeals to emotion - attach positive associations to the author’s argument and negative ones to his opponent’s position

Appeal to Probability

  • I see a dark cloud on the horizon. Dark clouds mean rain – uncertain (just probable)

Bad Reasons Fallacy or Argumentum Ad Logicam

  • Bad argument lead to bad conclusions

  • Dogs are afraid of heights; therefore, dogs do not fly.

  • Conclusion is true but reason is false

Masked Man Fallacy or Intentional Fallacy

  • Person’s get interchanged as they appear identical

  • Teacher who scolded and class teacher appear same – they are very strict and not good

Non Sequitur

  • Conclusion is not from propositions

  • All Dubliners are from Ireland. Ronan is not a Dubliner; therefore, he is not Irish.

  • We cannot comment on one who is not a Dubliner based on information.

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