troperville

tools

toys


main index

Narrative

Genre

Media

Topical Tropes

Other Categories

TV Tropes Org
random
Logical Fallacies
aka: Logical Fallacy
*Producers notice a fairly small sign blending in, reading "Flim Springfield"*
"This place must be hot. They don't need a big ad, or even correct spelling."
"Can't argue with that logic."
Radioactive Man Producers, on the topic of Springfield as a movie location, The Simpsons

Logic. Every story needs some of it, unless you just want a series of unconnected images and no plot to speak of.

The problem is that logic requires writers to think pretty hard about what they write, and not all writers have time or inclination to do so. So they take shortcuts, creating fallacies which at best can lead to plot holes or, at worst, undermine the entire story.

Fallacies are common errors in logic. By strict standards, fallacies don't address the truth of the premises or syllogism; they only address the validity of the logic, and as this page demonstrates, "truth" and "validity" are not the same thing when speaking of formal logic. There is a reason there are Critical Thinking classes.

Where deductive logic is valid, the conclusion must be true if the premises are true. "If it rains, then the sidewalk will be wet" is valid, so if you know that it rained, you know that the sidewalk will be wet. If you simply reverse the terms and say "if the sidewalk is wet, then it rained" this would not be valid (to correct this, you need to construct a "contra-positive," where you reverse the terms as well as negating them to get "if the sidewalk is not wet, then it did not rain").

However, inductive logic involves reasonable inferences of what might be true, but not necessarily. A sidewalk could be wet due to a passing street sweeping vehicle or neighbours carelessly watering their lawns. Seeing a wet sidewalk and concluding that there was rain is fallacious—not deductively valid—but it is not necessarily false, nor is it necessarily an unreasonable inference to make.

Logical fallacies are faulty deductive reasoning. This doesn't mean that they aren't effective at persuading. Many of them are extremely effective tools of persuasion. The key is that there are two primary routes of persuasion: the central (logical) route and the peripheral (emotional) route. To persuade someone using the central route, you need logic; a logical fallacy will make your argument fall flat on its face. To persuade someone using the peripheral route, you don't need logic; you simply need to play on their emotions. Some people are impassive to emotional appeals, and so you must use logic to persuade them; others are confused by logic, and so must be persuaded through emotion.

However, one must keep in mind that—depending on the surrounding circumstances—a deductively fallacious argument may still, none the less, be a reasonable and (inductively) logical argument that has decent prospects of being true despite the deductive logic being invalid. A classic example is if someone were to examine a million swans and note that all of them were white. It would be a (deductively) logical fallacy to conclude that "all swans are white". You could not make that conclusion unless you know that you had examined all swans in the universe. That doesn't make it illogical, however. If no one had ever seen a black swan, it might be rather sensible. Plus, this whole type of analysis is complicated when you talk about statistical trends. For these kinds of special cases, see Fallacy Fallacy.

For examples of characters falling into these fallacies (intentionally on the writer's part), see Insane Troll Logic and Chewbacca Defense. Not to be confused with Logic Bomb.
  • Ad Hoc: Mistaking an argument for an explanation.
  • Ad Hominem: Attacking the arguer or the argument's presentation instead of the actual argument.
  • Anecdotal Fallacy: Using a personal example as empirical evidence.
  • Appeal To Authority: Assuming something is true because an authority said it to be so OR calling someone an expert (and therefore correct) when they are not an actual expert.
  • Appeal to Consequences: Assuming something is correct/incorrect because of the positive/negative effects that will arise if it is implemented.
    • Appeal to Force: Threatening anyone who disagrees with you, and therefore claiming what you say is true. A species of the Appeal to Consequences.
    • Appeal to Fear: Saying bad things will happen to anyone who disagrees with you, and therefore what you say is true. A species of the Appeal to Consequences.
  • Appeal To Flattery: Claiming that a certain conclusion reflects well on anyone who agrees with it, or poorly on anyone who does not.
  • Appeal to Ignorance: Claiming something is true/false because it has never been proven false/true.
  • Appeal to Inherent Nature: Claiming something otherwise unacceptable is acceptable because it is within the nature of the doer to do it.
  • Appeal To Morality: Claming anything that is morally desirable is true/natural, and anything that is immoral is false/unnatural.
  • Appeal to Nature: Claiming anything that appears naturally is good, and anything that appears unnaturally is bad.
  • Appeal To Novelty: Claiming something is superior to something else because the first is newer.
  • Appeal to Obscurity: Attributing an argument to someone the other party doesn't know and using the fact that they aren't known as evidence.
  • Appeal To Pity: Claiming an argument is valid because either the arguer or an involved party deserves sympathy.
  • Appeal To Popularity: Claiming something is true because many or most people believe it.
  • Appeal To Ridicule: Claiming an argument is false by presenting it in an absurd fashion.
  • Appeal To Tradition: Claiming something is superior to something else because the first is older.
  • Appeal To Wealth: Claiming something is good because the rich or famous support it.
  • Appeal To Worse Problems: Claiming an argument isn't valid because there are bigger problems than it.
  • Argument of Contradictions: An argument that consists of nothing more than a shouting match — each side loudly repeating their side in turn.
  • Argumentum Ad Nauseam: Repeating an argument over and over until no one wants to dispute it anymore, then claiming it to be correct.
  • Argumentum Ad Lapidem: Dismissing an opposing argument as absurd without any sort of support.
  • Association Fallacy: Claiming "X is a Y. X is also a Z. Therefore, Y is a Z."
    • Hitler Ate Sugar: Claiming something is bad because an evil person (like Hitler) liked it. A species of the Association Fallacy.
  • Bandwagon Fallacy: Accept or adopt something simply because the majorities have already done so, regardless of actual validity or desirability.
  • Begging The Question: Mistaking the argument for the evidence. "People who use X are in danger of Y, because X can Y."
  • Bulverism: Rather than proving a statement wrong, assuming that it is wrong and then explaining why your opponent holds it.
  • Cab Driver's Fallacy: Being so devoted to meeting a quota that one tries too hard when there is little reward to be gained or doesn't try hard enough when great rewards are available.
  • Chewbacca Defense: Using non-sequitur arguments to prove a point, relying on distracting and confusing the opposition.
  • Circular Reasoning: Any argument where its conclusion is used as its premise.
  • Confirmation Bias: Presenting only data that supports your predetermined position and ignoring data that damages your position.
  • Converse Error: Concluding that a certain set of results can only come from one set of circumstances. "If A, then B. B, therefore A."
  • Correlation Implies Causation: Believing that any two variables that appear to work in tandem actually do work in tandem. "When X occurs, Y goes up. Therefore, Y must always go up when X occurs."
  • Extended Analogy: Comparing two issues as direct analogs, regardless of their relation. "You support X, which means you support Y."
  • Fallacy Fallacy: Because someone used a fallacy to argue a point, their premise must be incorrect.
  • Fallacy Of Composition: The properties of the parts are applied to the whole. "A is made of B. B is X, so A is X."
  • Fallacy Of Division: The properties of the whole are applied to the parts. "A is made of B. A is X, so B is X."
  • False Cause: Assuming that because one event came after another, that the first event must have caused the second.
  • False Dichotomy (Either/Or Reasoning): Offering a choice between two extremes, usually one desired and one not, and ignoring the possibility of other options.
  • Four Terms Fallacy (Syllogism): "God is love. Love is blind. Stevie Wonder is blind. Therefore, Stevie Wonder is God."
  • Frozen Abstraction
  • Gambler's Fallacy: Thinking that previous random events will have an effect on future random events. "Odds of winning are 1:20, I've played 19 times, I'm due for some good luck."
  • Genetic Fallacy: Dismissing or accepting something entirely on the basis of its origin.
  • Golden Mean Fallacy: Thinking that the "middle ground" between two points is the best option, even when it shouldn't apply.
  • Hard Work Fallacy: The argument that the desired outcome is purely the result of the effort put in by the individual, regardless of any other factors.
  • Historians Fallacy: When one assumes that a decision-maker had the same information and perspective as those analysing their decision(s) with the benefit of hindsight.
  • Hypostatization
  • Insane Troll Logic: An argument or premise that makes no logical sense whatsoever.
  • Irrelevant Thesis
  • Let's See You Do Better: Thinking that because one is not an authority on whatever he/she is criticizing, they're in no position to do so.
  • Loaded Words: Using words which appeal to emotions rather than to logic.
  • Many Questions Fallacy
  • Moving the Goalposts: Continually changing the requirements for a reward so that it is never obtained.
  • Nirvana / Perfect Solution Fallacy: Comparing actual things with unrealistic, idealized alternatives.
  • Non Sequitur Fallacy: Coming to a conclusion which is not supported by the facts or even has no relationship to the facts.
  • No True Scotsman: Redefining a category to not include something that the speaker doesn't want it to include, even though it does in fact include that thing.
  • Oven Logic: If you cook something by increasing the temperature, you think you can cook it faster, but disastrous results appear right after.
  • Presentism: Projecting present-day ideas and perspectives are anachronistically introduced into depictions or interpretations of the past.
  • Proof by Examples: Generalizing a category to match the properties of given examples. "3, 17, and 97 are prime numbers; all odd numbers are prime."
  • Prosecutors Fallacy: Rejecting an explanation on the basis that it relies on exceptional circumstances in favor of an equally exceptional, but personally desired, explanation.
  • Retrospective Determinism
  • Sharpshooter Fallacy: Forming theories that exactly match existing data, or "Painting the target around the bullet hole."
  • Shifting The Burden Of Proof: Arguing that something must be true (or false) because it has not been proven false (or true).
  • Slippery Slope Fallacy: Claiming that an action will inevitably lead to another, very unacceptable action. "If X, then eventually Y."
  • Special Pleading: Demanding an exception be made without justification or for a non-logical reason ("I can park in the handicapped spot because I'm a movie star!")
  • Spotlight Fallacy: "I've been hearing a lot about event X in the news lately, so event X must happen a lot." when it's only in the news because it's unusual.
  • Spurious Similarity: It is suggested that some relatively superficial resemblance is proof of a relationship.
  • Stolen Concept: Making an argument that rests upon (and conveniently ignores) contradictory, intrinsically self-refuting concepts.
  • Strawman Fallacy: Deliberately misrepresenting an opponent's argument by constructing it in such a way that it can be easily defeated.
  • Style Over Substance: When the arguer embellishes the argument with compelling language or rhetoric, and/or visual aesthetics.
  • Subjectivist Fallacy ("That's just your opinion"): When someone resists the conclusion of an argument not by questioning whether the argumentís premises support its conclusion, but by treating the conclusion as subjective when it is in fact objective.
  • Sunk Cost Fallacy ("Throwing good money after bad"): Assuming that because one has already invested time or money into something, it is worth continuing to do that thing even if it produces no gains.
  • Tautological Templar: "I'm a good guy so everything I do is good because I say so."
  • Two Negative Premises
  • Undistributed Middle

... And not fallacies but relevant-


"A foolish consistency is the hobgoblin of little minds, adored by little statesmen and philosophers and divines." (Ralph Waldo Emerson)
    Logic TropesAd Hoc
Loaded WordsThe Only Righteous Index of FanaticsLoners Are Freaks

alternative title(s): Logical Fallacy; You Fail Logic Forever
random
TV Tropes by TV Tropes Foundation, LLC is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License.
Permissions beyond the scope of this license may be available from thestaff@tvtropes.org.
Privacy Policy
29353
7