The 55-year-old Australian actress has been married to playwright and director Andrew Upton, 59, since 1997 and insisted that longevity should come with the "expectation" that each partner will never "truly know" the other.
"Yes, it's all about the things that are not said, which is really interesting to play," She told The Observer.
"I think it's a fascinating way to look at a marriage now because it's meant to be all about honesty, having everything out there.
"But what does that mean for desire and what does it actually mean for trust, if there are no secrets that you're prepared to keep?"
"Every marriage is different, but the ones that last are based on a profound trust and, I think, not having a stranglehold over your partner. Or an expectation, really, that you can ever truly know one another."
Meanwhile, the Tar actress - who has Dashiell, 23, Roman, 20, and Ignatius, 17 and 10-year-old Edith with her husband - insisted that just as the #MeToo movement came about, things were suddenly being "discredited and undermined" and that nearly a decade on from when it took place, she said women were "nowhere nearly equal pay" despite the campaign.
"Well, the conversation had just begun and suddenly everything was being discredited and undermined, so we're still having to fight for those same basic conversations."
She feels the industry has "definitely" gone backward since then.
"We're nowhere near equal pay! Talking about it noisily doesn't mean action has happened.
"I mean, there's a greater concentration of wealth than perhaps there ever has been in human history. And we can see where that's got us."
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