A case for the Third Universal Cardinal Rule of Thumb: Never be absolute, unless absolutely necessary.

A linguistics professor was lecturing to his class one day.

"In English," he said, "A double negative forms a positive.

In some languages, though, such as Russian, a double negative is still a negative.

However, there is no language wherein a double positive can form a negative."

A voice from the back of the room piped up, "Yeah, right."

Good one.

I had to think about that one for a few minutes. Good one!