Exclusive Premisses

Alias: Two Negative Premisses

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:

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.

Source:

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