An argument is fallacious when the reasons offered fail to warrant
acceptance of the conclusion. The fallacies in this section are
called formal fallacies because problems with the FORM or structure
of the argument mean that the conclusion is not certain. In other
words, whenever you encounter an argument using one of these
forms, there is cause to doubt the conclusion.
If P, then Q. Q. Therefore, P.
The symbolic form looks like this;
If it is raining, then it is cloudy. It is cloudy. Therefore,
it is raining.
Recall that whenever the antecedent is present, the consequent
necessarily follows. But it doesn't work the other way around.
The consequent's presence tells us nothing about the antecedent's
presence. Experience tells you that there are times when it is
cloudy (the consequent), but it is NOT raining. This shows that
it is possible for the premises of this type of argument to be
true and the conclusion to be false. Hence, it is not a valid argument