Also called Two Negative Premises.
A syllogism has two negative premises.
When both premises are negative, there is no connection between them, and nothing follows from them. This makes the argument invalid. A standard syllogism cannot have two negative premises.
No reptiles are mammals. No dogs are reptiles. Therefore, no dogs are mammals.
No Muslims are Christians. No Jews are Muslims. Therefore, no Jews are Christians.
Even if the conclusion is correct, the 'reasoning' is fallacious.