Introduction

• Gottlob Frege, a key 19th Century logician, stressed the job of a logician is to distinguish correct reasoning from flawed reasoning and identify how language can mislead thought.

• A fallacy is an error in reasoning where premises fail to support the conclusion. Example:

  • “This man is not intelligent because he cannot run fast” is fallacious—speed isn’t logically linked to intelligence.

• Logic uses axioms to govern arguments, and violating them results in fallacies and invalid arguments.

• Example of formal fallacy:

  • P1: All whales are mammals.

  • P2: X is a mammal.

  • C: X is a whale.

  • That conclusion is invalid—not all mammals are whales—highlighting a formal fallacy, i.e. error in argument structure.

• This unit focuses on informal fallacies, which arise from content-based errors, often linked to language use.

• Everyday language introduces ambiguity, imprecision, and obscurity, resulting in informal fallacies.

• Causes of informal fallacies:

  • Incomplete context understanding.

  • False assumptions or misinterpretations.

  • Distraction, bias, or emotional influence.

  • Overgeneralization without adequate evidence.

  • Preconceived notions/prejudices.

• Importance of logical awareness: helps in identifying and avoiding such reasoning errors.

• Caution: Not all seemingly fallacious language—like sarcasm, metaphor, or irony—indicates flawed logic; context matters.