This is a short excerpt from 'Ring around the moon', a play by Jean Anouilh. I love this short conversation, it is relevant today even more:
ROMAINVILLE: For God's sake, she isn't my mistress! I assure you she isn't, not the least bit.
HUGO: Who's going to believe you?
ROMAINVILLE: Everybody - because it's true.
HUGO: That's no help. It doesn't seem likely.
ROMAINVILLE: So according to you the truth means nothing.
HUGO: Nothing, dear boy, if no one believes it.
It could be said today but even more, Philip Marlowe could have said it and it would have made perfect sense. The authorities in Japan know this (but probably regret not learning more about it) and I think a lot of people are still trying to learn what this really means.