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In philosophy, a logical fallacy or a formal fallacy is a pattern of reasoning which is always or at least most commonly wrong. This is due to a flaw in the structure of the argument which renders the argument invalid. A formal fallacy is contrasted with an informal fallacy, which has a valid logical form, but is false due to one or more of its premises being false.

The term fallacy is often used more generally to mean an argument which is problematic for any reason, whether it be a formal or an informal fallacy.

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 is one way to reduce the likelihood of such occurrences.

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.

These fallacies are used in many forms of modern communication where the intention is to influence behavior and change beliefs. Examples in the mass media today include but are not limited to propaganda, advertisements, politics, and opinion news shows.

Contents 1 Common examples 2 See also 3 References 4 External links

• Formal fallacies
  • Argument from fallacy "ad logicam"
  • Affirming the consequent or Denying the antecedent
• Faulty generalization Inductive fallacies like
  • Biased sample
  • Half-truths
  • Hasty generalization
  • Misleading vividness
  • Package-deal fallacy or False dilemma
  • Proof by example
• Questionable cause Informal causal fallacies
  • Begging the question, circular logic "petitio principii"
  • Correlation implies causation "Cum hoc ergo propter hoc"
  • Post hoc ergo propter hoc
  • Appeal to consequences "ad consequentiam"
  • Appeal to force "ad baculum"
  • Appeal to probability & Slippery slope
• Informal Relevance fallacies
  • Irrelevant conclusion "Ignoratio elenchi" like Red herring
  • Straw man
  • Association fallacy
  • Ad hoc
  • Argument from ignorance, incredulity, belief, conviction... "ad ignorantiam"
  • Appeal to emotion like Appeal to fear, Appeal to flattery, Appeal to pity, Appeal to nature, Appeal to spite...
  • Wishful thinking
  • Appeal to authority or Appeal to ridicule
  • "Ad hominem" — Attacking the person rather then the argument
  • Appeal to the majority "ad populum"
  • Appeal to tradition "ad antiquitatem"
• Informal Verbal fallacies
  • Equivocation & Loki's Wager
  • Undistributed middle & No true Scotsman

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).

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

Formal fallacies v • d • e
Argument from fallacy | Fallacy of modal logic | Masked man fallacy | Appeal to probability
Fallacy of propositional logic:
	Affirming a disjunct | Affirming the consequent | Commutation of Conditionals Denying a conjunct | Denying the antecedent | Improper Transition
Fallacy of quantificational logic:
	Existential fallacy | Illicit Conversion | Quantifier shift | Unwarranted contrast
Syllogistic fallacy:
	Affirmative conclusion from a negative premise | Negative conclusion from an affirmative premise Exclusive premisses | Necessity | Four-term Fallacy | Illicit major | Illicit minor | Undistributed middle
Other types of fallacy

• 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.
• Vincent F. Hendricks, Thought 2 Talk: A Crash Course in Reflection and Expression, New York: Automatic Press / VIP, 2005, ISBN 87-991013-7-8
• 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.
• T. Edward Damer. Attacking Faulty Reasoning, 5th Edition, Wadsworth, 2005. ISBN 0-534-60516-8
• Sagan, Carl, "The Demon-Haunted World: Science As a Candle in the Dark". Ballantine Books, March 1997 ISBN 0-345-40946-9, 480 pgs. 1996 hardback edition: Random House, ISBN 0-394-53512-X, xv+457 pages plus addenda insert (some printings).

• Logical Fallacies — a semi-ordered list with definitions
• The Fallacy Files by Gary N. Curtis — real examples posted regularly.
• ESGE Logical Fallacies — European Society for General Semantics
• Logical Fallacies .Info
• Bruce Thompson's Fallacy Page
• Stephen Downes Guide to the Logical Fallacies
• Logical Fallacies and the Art of Debate
• Logic & Fallacies: Constructing a Logical Argument
• Logical Fallacies Quiz Ten common fallicies in an interactive test format.
• Humbug! Online List of fallacies with links to real examples — posted regularly.
• 42 informal logical fallacies explained by Dr. Michael C. Labossiere, including examples.
• On Informal Fallacies is a collection of one-off fallacies coined for specific, rhetorical purposes.
• Marilyn vos Savant explains Logical Fallacies
• Some paradoxes — an anthology