Example Logical Fallacies Used in Reasoning

A remarkably large number of logical fallacies used in reasoning and arguments has been identified.  Following is a partial list of such fallacies.  More complete information on logical fallacies is available in the two references below.  It is important to recognize logical fallacies when they are being used, particularly for persuasive purposes.  Once identified, the fallacy should be corrected and the argument repaired with non-faulty reasoning.

I suggest that an interesting avenue for artificial intelligence research to pursue would be a set of tools to aid human thinkers in identifying and correcting logical fallacies.  This would be an extension of current writing assistance tools that provide spell checking, grammar checking, punctuation checking, and the like.  The tools could be used both by original authors and by those reviewing work by others.

In a case where artificial intelligence systems are being used for making choices and decisions, the reasoning involved should be examined by the systems to identify and flag possible logical fallacies.

  • Faulty reasoning (non sequitur, “it does not follow”): a conclusion in an argument that does not follow from the previous statements:
  • Faulty analogy: using weak comparisons to make a point rather than using deductive and inductive reasoning.
  • Personal attack (argumentum ad hominem, “argument toward the man”): a rejection or criticism of an opponent’s position in a discussion based on personal characteristics, appearance, background, or other features irrelevant to the matter at hand.
  • Misleading statistics: using statistics improperly to make a point (e.g., ones with a non-representative sample).
  • Straw man: an attack on a position an opponent doesn’t really hold—an easily-defeated effigy that the opponent never intended to defend. Being able to knock down the straw man discredits the opponent and raises the position of the attacker.
  • Appeal to ignorance (argumentum ad ignorantium: “argument from ignorance”): the use of the lack of information as a major premise in support of an argument. If the non-existence of flying saucers has not been proven, that is neither proof that they exist or that they don’t exist.
  • False dichotomy: the options are limited to two when in fact other alternatives exist. This is often used to polarize the audience by making the only alternative option presented highly unattractive.  “We must go to war, or be seen as weak”.
  • Slippery slope: from a seemingly benign premise or starting point, a series of small steps are described leading to an unlikely extreme.
  • Circular reasoning/begging the question (petitio principii): concluding what was already assumed at the beginning, as though it were proven.
  • Hasty generalization (dicto simpliciter): general statements made without sufficient evidence to support them. Cases include exaggerations, overstatements, stereotypes, and unwarranted conclusions.
  • Red herring: a red herring is a distraction thrown into the discussion that superficially appears to be relevant but in fact is off-topic. It is often used to detour into something that is easier or less threatening to address.
  • What about you? (tu quoque,“you too”): a diversionary tactic of pointing out hypocrisy in an opponent. It is used to deflect criticism away from one’s self by accusing one’s opponent of the same or a comparable defect.
  • Causal fallacies:
    • False cause (non causa pro causa, “not the cause for a cause“): concluding about a cause without sufficient evidence.
    • Post hoc, ergo propter hoc (“after this, therefore because of this“): mistaking something for the cause simply because it came before. Superstitions are common examples of this fallacy.
    • Correlational fallacy: mistaking that two things found together are causally related. Correlation does not imply causation.
  • Appeal to improper authority (argumentum ad verecundium): citing authorities to make one’s case, without sufficient evidence that the authorities are relevant and knowledgeable/competent in the matter being discussed, particularly when alternative convincing evidence is available. The view of the authority may only be an opinion.
  • Equivocation: using a word, phrase, or sentence with the intent to confuse, deceive, or mislead by appearing to have one meaning but actually meaning something else. Using the euphemism “creative license” in place of “lying” is an example.
  • Appeal to emotion (argumentum ad misericordiam, “argument from pity”): using emotional manipulation to sway an argument, so that feelings are mistaken for facts.
  • Appeal to force (argumentum ad baculum): using the threat of some unpleasant action or outcome to make the audience concede or accept a conclusion.
  • Appeal to tradition (argumentum ad traditionem): using the fact that something is traditional as an argument for its correctness.
  • Bandwagon fallacy: asserting that something is true or right, or good because other people are agreeing with it. The broad acceptance of something is not necessarily an indication that such acceptance is warranted.
  • Irrelevant conclusion (ignorantio elenchi): concluding something that is irrelevant to the subject under consideration.
  • Appeal to the stone (argumentum ad lapidum): dismissing a claim as absurd without demonstrating its absurdity.
  • Argument from incredulity: saying that one cannot imagine the claim to be true, so it must be false.
  • Loaded question: phrasing a question so as to imply another unproven statement is true without evidence or discussion.
  • Stacking the deck: ignoring the examples that disprove the point and covering only those that support the argument.
  • Argument from the negative: asserting since one position is untenable, the opposite must be true.
  • Undistributed middle term: an error in deductive reasoning in which the minor premise and the major premise of a syllogism may or may not overlap.
  • Contradictory premises (logical paradox): putting forward one premise that contradicts another, earlier premise.
  • Composition fallacy: reasoning from the properties of the parts of the whole to the properties of the whole itself.
  • Division fallacy: reasoning that what is true for the whole is true for the parts of the whole.
  • Reification fallacy: treating an abstraction or process as equivalent to a concrete object or thing.
  • Hypothesis contrary to fact (argumentum ad speculum): asserting that, if hypothetically X had occurred, Y would have been the result.
  • Sunk cost fallacy: continuing with a task or project because of what has been invested already, without considering the future costs of continuing and the diminishing benefits

See also references on logical fallacies:



1 thought on “Example Logical Fallacies Used in Reasoning”

  1. What a great list, thank you! I suspect we can all identify having seen (or worse, used) items from this list.

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