Affirming the Consequent, Denying the Antecedent.

Even if both premises are true, the syllogism may still be invalid.

Antecedent

Consequent

Affirming the Antecedent (correct)

If A

If I work at Victoria's Secret

Then B

I must be sixteen or older.

A

I work at Victoria's Secret

Then B

Therefore I am over sixteen.

 

 

Denying the Consequent (correct)

If A

If I work at Victoria's Secret

Then B

I must be sixteen or older.

Not B

I am not yet sixteen

Then Not A

I do not work at Victoria's Secret

 

 

Affirming the Consequent (incorrect)

If A

If I work at Victoria's Secret

Then B

I must be sixteen or older.

B

I am over sixteen

Then A

I work at Victoria's Secret

 

 

Denying the Antecedent
(incorrect)

If A

If I work at Victoria's Secret

Then B

I must be sixteen or older.

Not A

I do not work at Victoria's Secret

Then Not B

Therefore I am not yet sixteen

 

 

If I am a student at Wake Forest, then I am in college.

If I am eating shrimp, I am eating seafood.

If I am driving a Lexus, I am driving an automotive vehicle.

If I am at the Louvre, I am in Paris.

If McCain wins in South Carolina, he will win the nomination.

If I work at Victoria's Secret, then I am sixteen or older.

If I have eaten spaghetti, I must like Italian.

If my birthday is July 16, my sign is Cancer.

If play in the ACC, then I am a division I athlete.