Syllogistic Fallacies

Disciplines > Argument > Fallacies > Syllogistic Fallacies

A syllogism is an argument that has a major premise, a minor premise and a conclusion, and often appears in the form 'A is B, C is D, therefore E is F'. This is a specific form of argument with very specific rules that are easy to break. In many ways, syllogistic fallacies are the 'classic' form of fallacy.

• Affirming the Consequent: If A then B. B is true, so A is true.
• Denying the Antecedent: If A then B. A is false, so B is false.
• Four Terms: All A is B. All C is D. So all A is D.
• Illicit Major: All X is Y. No P (which is a subset of Y) is X. Therefore no P is Y.
• Illicit Minor: All X are Y. All X are P. Therefore all P are Y.
• Undistributed Middle: All A is B. All C is B. Therefore all C is A.

See also

Non-sequitur Fallacies, Statistical Fallacies