Bias List

Syllogistic Fallacies

affirmative-conclusion-from-a-negative-premise

Affirmative Conclusion from a Negative Premise

A formal fallacy that is committed when a categorical syllogism has a positive conclusion, but one or two negative premises.For example:"No fish are dogs, and no dogs can fly, therefore all fish can fly." The only thing that can be properly inferred from these premises is that some things that are not fish cannot fly, provided that dogs exist.

fallacy-of-exclusive-premises

Fallacy of Exclusive Premises

Committed in a categorical syllogism that is invalid because both of its premises are negative. For example: "No cats are dogs. Some dogs are not pets. Therefore, some pets are not cats."

fallacy-of-four-terms

Fallacy of Four Terms

Occurs when a syllogism has four (or more) terms rather than the requisite three. This form of argument is thus invalid.

illicit-major

Illicit Major

Invalid because its major term is undistributed in the major premise but distributed in the conclusion. This fallacy has the following argument form: "All A are B. No C are A. Therefore, no C are B."

illicit-minor

Illicit Minor

Invalid because its minor term is undistributed in the minor premise but distributed in the conclusion. This fallacy has the following argument form: "All A are B. All A are C. Therefore, all C are B."

negative-conclusion-from-affirmative-premises

Negative Conclusion from Affirmative Premises

Committed when a categorical syllogism has a negative conclusion yet both premises are affirmative. The inability of affirmative premises to reach a negative conclusion is usually cited as one of the basic rules of constructing a valid categorical syllogism.

undistributed-middle

Undistributed Middle

Committed when the middle term in a categorical syllogism is not distributed in either the minor premise or the major premise. For example: "All Z is B. All y is B. Therefore, all y is Z." B is the common term between the two premises (the middle term) but is never distributed, so this syllogism is invalid.