Rain Rain Go Away .................

Now a day, every time at 4pm will rain heavily. I very lazy to bring sweater and umbrella along. But if I don't bring the umbrella along then I will be caught in the rain. I will not be caught in the rain. Therefore, I had to bring along the umbrella.

Common Pattern - Deductive - Hypothetical(Modus Tollens)
*denying the consequent*

If A then B.
Not B.
Therefore, not A.