Logical fallacies

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In philosophy, the term logical fallacy properly refers to a formal fallacy: a flaw in the structure of a deductive argument which renders the argument invalid. However, it is often used more generally in informal discourse to mean an argument which is invalid for any reason, and thus encompasses informal fallacies – those which are invalid for reasons other than structural flaws, such as an error in the premises – as well as formal fallacies.

The presence of a formal fallacy in a deductive argument does not imply anything about the argument's premises or its conclusion. Both may actually be true, or even more probable as a result of the argument (e.g. appeal to authority), but the deductive argument is still invalid because the conclusion does not follow from the premises in the manner described. By extension, an argument can contain a formal fallacy even if the argument is not a deductive one; for instance an inductive argument that incorrectly applies principles of probability or causality can be said to commit a formal fallacy.

Recognizing fallacies in everyday arguments may be difficult since arguments are often embedded in rhetorical patterns that obscure the logical connections between statements. Informal fallacies may also exploit the emotions or intellectual or psychological weaknesses of the audience. Having the capability to recognize fallacies in arguments will hopefully reduce the likelihood of such an occurrence.

A different approach to understanding and classifying fallacies is provided by argumentation theory; see for instance the van Eemeren, Grootendorst reference below. In this approach, an argument is regarded as an interactive protocol between individuals which attempts to resolve a disagreement. The protocol is regulated by certain rules of interaction and violations of these rules are fallacies. Many of the fallacies in the list below are best understood as being fallacies in this sense.

Common examples

• Ad baculum
• Ad hominem
• Affirming the consequent
• Appeal to authority
• Appeal to fear
• Appeal to pity
• Appeal to tradition
• Appeal to probability
• Appeal to the majority
• Argument from ignorance
• Begging the question
• Biased sample
• Correlation implies causation
• Equivocation
• Hasty generalization
• Post hoc ergo propter hoc
• Straw man

For a list of types of formal and informal fallacy, as well as examples of fallacious arguments, see Fallacy. For a concise list of "appeal to" fallacies, see Appeal (disambiguation).

See also

• Anecdotal evidence
• Cogency
• Cognitive bias
• Demagogy
• Fallacies of definition
• False statement
• Informal logic
• Invalid proof
• Paradox
• Sophism
• Soundness
• Spurious relationship
• Validity
• Vacuous truth

References

• Aristotle, On Sophistical Refutations, De Sophistici Elenchi.
• William of Ockham, Summa of Logic (ca. 1323) Part III.4.
• John Buridan, Summulae de dialectica Book VII.
• Francis Bacon, the doctrine of the idols in Novum Organum Scientiarum, Aphorisms concerning The Interpretation of Nature and the Kingdom of Man, XXIIIff.
• The Art of Controversy | Die Kunst, Recht zu behalten - The Art Of Controversy (bilingual), by Arthur Schopenhauer
• John Stuart Mill, A System of Logic - Raciocinative and Inductive. Book 5, Chapter 7, Fallacies of Confusion.
• C. L. Hamblin, Fallacies. Methuen London, 1970.
• Fearnside, W. Ward and William B. Holther, Fallacy: The Counterfeit of Argument, 1959.
• D. H. Fischer, Historians' Fallacies: Toward a Logic of Historical Thought, Harper Torchbooks, 1970.
• Douglas N. Walton, Informal logic: A handbook for critical argumentation. Cambridge University Press, 1989.
• F. H. van Eemeren and R. Grootendorst, Argumentation, Communication and Fallacies: A Pragma-Dialectical Perspective, Lawrence Erlbaum and Associates, 1992.
• Warburton Nigel, Thinking from A to Z, Routledge 1998.

External links

• The Fallacy Files by Gary N. Curtis
• Logical Fallacies .Info
• Bruce Thompson's Fallacy Page

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