

Definition 
Also called Confusing A Necessary With A Sufficient Cause.
Any argument of the following form is invalid: If p_{1} then p_{2}; notp_{1}; therefore, notp_{2}.
Explanation 
This is mathematically incorrect. p_{1} is a sufficient cause of p_{2} and that means that if we have notp_{2}, we can conclude that we have notp_{1} (the negation of "if p_{1} then p_{2}"). But having notp_{1} is not enough to conclude that we have notp_{2}.
Examples 
If you get hit by a car when you are six then you will die young. But you were not hit by a car when you were six.
Thus you will not die young.
Of course, you could be hit by a train at age seven, in which case you still die young.
If I am in Calgary then I am in Alberta. I am not in Calgary, thus, I am not in Alberta.
Counterexamples 
None.
Advices 
Show that even though the premises are true, the conclusion may be false. In particular, show that the consequence p_{2} may occur even though p_{1} does not occur.