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Syllogistic Fallacies The fallacies in this section are all cases of invalid categorical syllogisms. Readers not familiar with categorical syllogisms should consult Stephen's Guide to Categorical Syllogisms. The following are syllogistic fallacies: Fallacy of Four Terms: a syllogism has four terms Undistributed Middle: two separate categories are said to be connected because they share a common property Illicit Major: the predicate of the conclusion talks about all of something, but the premises only mention some cases of the term in the predicate Illicit Minor: the subject of the conclusion talks about all of something, but the premises only mention some cases of the term in the subject Fallacy of Exclusive Premises: a syllogism has two negative premises Fallacy of Drawing an Affirmative Conclusion From a Negative Premise: as the name implies Existential Fallacy: a particular conclusion is drawn from universal premises 25 May 1995 For Educators Stephen Downes Guide to the Logical Fallacies Copyright © Stephen Downes, 1995-2001 stephen.downes@ualberta.ca