Negative Conclusion from Affirmative Premisses

Alias:
  • Illicit Negative/Affirmative
  • Positive Conclusion/Negative Premisses
Type: Syllogistic Fallacy

Form:

Any form of categorical syllogism with a negative conclusion and affirmative premisses.

Example Counter-Example
All sound arguments are valid.
Some fallacious arguments are sound.
Therefore, some fallacious arguments are not valid.		 All dogs are animals.
Some pets are dogs.
Therefore, some pets are not animals.
Venn diagram

Venn Diagram:

This diagram shows that both the Example and Counter-Example are invalid, since it does not show that there is anything in the area with the question mark.

Syllogistic Rule Violated:

Any validating form of categorical syllogism with both premisses affirmative has an affirmative conclusion.

Source:

Robert Audi (General Editor), The Cambridge Dictionary of Philosophy (Second Edition), 1995, p. 272.

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