Category:Logical Fallacies

"*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 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, and 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 'contrapositive' 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 zealously and carelessly watering their lawns. Seeing a wet sidewalk and concluding that there was rain is fallacious - not deductively valid - but it is not necessarly 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 upon 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 where 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 examples of writers intentionally failing logic forever, see Insane Troll Logic and Chewbacca Defense. Not to be confused with Logic Bomb.


 * Wanted Fallacies -- delete as pages are made and added below
 * Historian's Fallacy
 * Presentism
 * Intentional Fallacy
 * Kettle Logic
 * Mind Projection Fallacy
 * Moralistic Fallacy
 * Nirvana Fallacy:


 * And not fallacies but relevant:
 * Occam's Razor
 * Hanlon's Razor: Don't assume malicious intent when stupidity could do.
 * Sound, Valid, True