The Implications of Logic by Sandra DeLozier Coleman
That p --> q is true,
Doesn’t say very much about q.
For if p should be false,
Then there’s really no loss
In assuming that q could be, too.
On the other hand q could be true.
So, what is a body to do?
With a false antecedent,
The consequent needn’t
Be something one lends credence to!
If the whole statement’s false, then, my dear,
There is no ambiguity here!
For then p must be true,
But then not so for q.
I do hope that’s all perfectly clear!