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Logical Fallacies


Analogy   A comparison of things that are claimed to be similar in some respect, 70, 175, 323, 423
Appeal to ignorance   A fallacy that occurs when an arguer claims that something is true because no one has proven it false, or that something is false because no one has proven it true, 166--168, 187
Authority   A person who possesses special knowledge, competence, or expertise in a particular field, 163
Biased sample   A set of observed cases that is not typical or representative of the larger population from which it was selected, 173
Fallacies of insufficient evidence   Fallacies that occur because the premises, though logically relevant to the conclusion, fail to provide sufficient evidence to support the conclusion, 140, 162-188
False alternatives   A fallacy that occurs when an arguer poses a false either/or choice, 168--169
Generalization   A statement that asserts that all or most things of a certain kind have a certain property or characteristic. Also, in statistics, a statement of the form "A certain percentage of all A's are B's," 67, 172
Hasty generalization   A fallacy that occurs when an arguer draws a general conclusion (i.e., a conclusion of the form "All A's are B's" or "Most A's are B's") from a sample that is biased or too small, 172--173, 188, 310
Inappropriate appeal to authority   A fallacy that occurs when an arguer appeals to a witness or alleged authority that is unreliable, 162--166
Inconsistency   A fallacy that occurs when an arguer asserts conflicting or contradictory claims, 177--178, 188; logical versus practical, 4
Loaded question   A fallacy that occurs when an arguer poses a question that contains an unfair assumption or presupposition, 170-171
Mere correlation fallacy   A fallacy that occurs when an arguer assumes, without sufficient evidence, that because A and B regularly occur together, A must be the cause of B, or vice versa, 171--172
Oversimplified cause fallacy   A fallacy that occurs when an arguer assumes, without sufficient evidence, that A is the sole cause of B, when in fact there are several causes of B, 172
Post hoc fallacy   A fallacy that occurs when an arguer assumes without sufficient evidence that because one event, A, occurred before another event, B, that A is the cause of B, 171
Questionable cause   A fallacy that occurs when an arguer claims without sufficient evidence that one thing is the cause of something else, 171--172, 334--335
Slippery slope   A fallacy that occurs when an arguer claims, without sufficient evidence, that a seemingly harmless action, if taken, will lead to a disastrous or very negative outcome, 173-174, 188
Weak analogy   A fallacy that occurs when an arguer's conclusion depends on a comparison of things that aren't relevantly similar, 175--177, 188, 326