The opposite of maybe

Yesterday, as I drove my six-year-old son home from school, he asked me a question.

"What's the opposite of maybe?"

I thought hard for a minute and answered, "I don't think 'maybe' has an opposite. It's kind of half-way between 'yes' and 'no'."

"I think the opposite of maybe is 'maybe not'," he replied.

Maybe my son is smarter than I am ...