Informal fallacy

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An informal fallacy is an argument whose stated premises fail to support its proposed conclusion.[1] The problem with an informal fallacy often stems from a flaw in reasoning that renders the conclusion unpersuasive. In contrast to a formal fallacy of deduction, the error is not merely a flaw in logic.

Formal deductive fallacies and informal fallacies[edit]

Formal fallacies of deductive reasoning fail to follow the rules of logic that guarantee a true conclusion follows given the truth of the premises. This is said to render the argument invalid.

Inductive fallacies are not formal in this sense. Their merit is judged in terms of rational persuasiveness, inductive strength or methodology (for example, statistical inference). For instance, the fallacy of hasty generalization, can be roughly stated as an invalid syllogism:

  1. A is an X
  2. A is also a Y
  3. Therefore, all Xs are also Ys

While never a valid deduction, if such an inference can be made on statistical grounds, it may nonetheless be convincing.

See also[edit]

Main article: List of fallacies


  1. ^ Kelly, D. (1994) The Art of Reasoning. W W Norton & Company, Inc. ISBN 0-393-96466-3

Further reading[edit]

External links[edit]