13. Informal Fallacies - Presumption Part 1

 

Summary

This begins the last and largest family of informal fallacies: the fallacies of presumption, which occur when an argument presupposes something without good reason or sufficient evidence, so the conclusion rests on an unproven or questionable assumption. The category splits into ordinary presumption fallacies and those tied to inductive reasoning. This first session introduces the family and covers the "stacking the deck" subgroup, biasing an argument toward your own conclusion via a hidden assumption. Seven are presented.

1. Petitio principii (begging the question / circular reasoning)

Assuming what you are trying to prove. The conclusion is smuggled into the premises, so you start and end in the same place. Forms include a conclusion that merely restates a premise, a chain whose final conclusion is the first premise, or premises whose language already implies the conclusion. (Note: in philosophy "begging the question" means this, not "raising a further question." Circular arguments are trivially valid by the law of identity, A implies A, but practically useless.) Example: macroevolution is proven by anatomical similarities, while those similarities are taken as proof of the evolutionary relationship.

2. Complex / loaded question

A question that presupposes an answer to an unstated, often false, question, and is loaded with assumptions that put the respondent in a bad light. The classic: "Have you stopped beating your wife?", yes or no both incriminate. Restricting answers to yes/no makes the trap tighter ("do you still have the gun you used to murder the victim?").

3. Loaded definition

Defining a term in an unjustified way (too broad, too narrow, or vague) so it smuggles in the conclusion. Example: "murder is the killing of innocent life, so eating animals is murder", a definition so broad it backfires even on the vegetarian using it.

4. Special pleading / suppressed evidence

Preventing the opposing view from getting a fair hearing, either by applying different standards to your opponent's argument than to your own, or by presenting only the evidence that supports your position (the suppressed-evidence variant, essentially confirmation bias). Example: the used-car pitch that lists the good points while omitting the price markup and slipping transmission.

5. Stacking the deck (proper)

Declaring the winner to be whoever meets standards you set so that only your own side can meet them. Unlike special pleading (different standards for each side), here the same standard is applied but only one argument can satisfy it. Example: "Superman is a better hero than Batman, Batman can't fly without a machine."

6. No true Scotsman

Reinterpreting evidence to shield a generalization from counter-examples by redefining the group to exclude them (from Antony Flew's example: "no true Scotsman would do that"). Example: "socialism caused poverty everywhere it was tried", "those weren't true socialist governments."

7. Slippery slope (domino fallacy)

Rejecting A because it will supposedly trigger an inevitable chain A → B → C → D ending in disaster. It is fallacious when the asserted chain is not actually necessary; the test is whether each causal/logical link is real or merely psychologically persuasive. (Arguments that genuinely show probable consequences are not fallacies.) Example: "drinking leads to marijuana, then crack, then suicide."

Where this leads

This is only the first of several presumption videos. The next covers the oversimplification / reduction subgroup, before the course moves into presumption fallacies specific to inductive reasoning.