

Definition 
Also called Confusing A Sufficient With A Necessary Cause.
Any argument of the following form is invalid: If p_{1} then p_{2}; p_{2}; therefore p_{1}.
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 p_{2} is not enough to conclude that we have p_{1}.
Examples 
If I am in Calgary, then I am in Alberta. I am in Alberta, thus, I am in Calgary.
Of course, even though the premises are true, I might be in Edmonton, Alberta.
If the mill were polluting the river then we would see an increase in fish deaths. And fish deaths have increased. Thus, the mill is polluting the river.
Counterexamples 
None.
Advices 
Show that even though the premises are true, the conclusion could be false. In general, show that p_{2} might be a consequence of something other than p_{1}. For example, the fish deaths might be caused by pesticide runoff, and not the mill.