I mean, it's fine when you're a kid and someone runs into the playground and goes, 'I've got this great game of pretend,' and you play... As an actor, getting to play, getting to use your imagination and be childish - it is weird but it's wonderful.
What convinces is conviction. Believe in the argument you're advancing. If you don't you're as good as dead. The other person will sense that something isn't there, and no chain of reasoning, no matter how logical or elegant or brilliant, will win your case for you.