Exclusive Premisses

Alias: Two Negative Premisses

Type: Syllogistic Fallacy

Form: Any form of categorical syllogism with two negative premisses.

Example Counter-Example
No moslems are christians.
No jews are moslems.
Therefore, no jews are christians.
No reptiles are mammals.
No dogs are reptiles.
Therefore, no dogs are mammals.
Venn diagram

Venn Diagram:

This diagram represents both the Example and Counter-Example, which it shows to be invalid, since the area with the question mark is not shown to be empty.

Syllogistic Rule Violated:

At least one premiss of a valid categorical syllogism is affirmative.


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