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Two Negative Premises

Two Negative Premises:

If A is not B, and B is not C, then A is C. This is always invalid logic (although it may happen to be true), as it is not possible to make a valid conclusion from two negative premises; logic is not arithmetic. This is a fallacy because simply identifying what something isn't doesn't identify what it is.

No Jews are Muslims.
No Muslims are Christians.
Therefore Jews are Christians.

No dogs are reptiles.
No reptiles are magenta.
Dogs are magenta.

No dogs are reptiles.
No reptiles shoot lasers out of their eyes.
Dogs shoot lasers out of their eyes.

Tautological TemplarLogical FallaciesUndistributed Middle
The Two Certainties In BritainAdministrivia/Useful Notes Pages in MainTypes Of Nuclear Weapons
Sunk Cost FallacyLogic TropesUndistributed Middle

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