Fallacies are Statements that Contain Errors of Logic or Language

A fallacy is an argument that may be persuasive but contains an error of logic or language.

A fallacy is an error in reasoning, but reasoning can be erroneous in a number of ways, so there is no definitive type of fallacy.

Greek Philosopher Aristotle The Greek Philosopher Aristotle (384–322 BCE) was the first to gather and explain the most common types of errors in reasoning, such as equivocation, begging the question, and false cause.

Aristotle wrote in On Sophistical Refutations (c. 350 BCE)


In the subsequent centuries of philosophical debate, new categories of fallacies were identified, and the philosophers William of Ockham and John Buridan compiled an extensive number of fallacy types, giving them Latin names such as argumentum ad populum (appeal to the people) and argumentum ad baculum (appeal to the stick, or force).

There are now more than 200 named fallacies, commonly divided between formal and informal.

  • Formal fallacies are mistakes in the logical form of an argument, independent of its semantic content. For example, in the non-fallacious form called Modus Ponens, a correct deduction can be derived from a conditional premise and a correct antecedent, regardless of the content. However, in the related formal fallacy called “affirming the consequent,” a false deduction is derived from the same correct conditional premise and a false antecedent. It follows that not every instance of the deduction would be true, even if the premise statements appeared correct individually.
  • An informal fallacy occurs when the content or organization of the premises of an argument constitutes an error in reasoning, as when an arguer changes the subject (red herring) or appeals to an inappropriate authority (argumentum ad verecundiam).
Posted in Mental Models and Psychology Philosophy and Wisdom

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