Christopher Nolan has discussed the controversial and ambiguous ending to his film Inception, which saw a spinning top rotating and wobbling a little before cutting to black.

Unsurprisingly, he didn't just say "it was all a dream" and then drop the mic, but gave a more nuanced explanation of what it was intended to symbolise, during a speech made to a graduating Princeton University class.

He started off with a pre-amble about pragmatism:

"In the great tradition of these speeches, generally someone says something along the lines of 'Chase your dreams,' but I don’t want to tell you that because I don’t believe that. I want you to chase your reality.

"I feel that over time, we started to view reality as the poor cousin to our dreams, in a sense….I want to make the case to you that our dreams, our virtual realities, these abstractions that we enjoy and surround ourselves with - they are subsets of reality."

According to The Hollywood Reporter, he then went on to link this idea to the conclusion of Inception:

"The way the end of that film worked, Leonardo DiCaprio’s character Cobb — he was off with his kids, he was in his own subjective reality. He didn’t really care anymore, and that makes a statement: perhaps, all levels of reality are valid. The camera moves over the spinning top just before it appears to be wobbling, it was cut to black.

"I skip out of the back of the theater before people catch me, and there’s a very, very strong reaction from the audience: usually a bit of a groan. The point is, objectively, it matters to the audience in absolute terms: even though when I’m watching, it’s fiction, a sort of virtual reality. But the question of whether that’s a dream or whether it’s real is the question I’ve been asked most about any of the films I’ve made. It matters to people because that’s the point about reality. Reality matters."

It's an elegant and thought-provoking explanation, though perhaps not as clear cut as some would like.

Then again, they never are. Sopranos creator David Chase has been asked to explain his big cut-to-black ending repeatedly for a decade now, and rightly insists that its beauty lies in its ambiguity and lack of closure.