The Spinning Top

The last image is Cobb's spinning top. If it keeps spinning, he is still dreaming; if it topples, he is awake. The camera cuts to black just before we can tell. That cliffhanger is not a cheap trick. It is the whole point: once you go deep enough, asking "dream or real?" stops being the question that matters.

Cobb does not wait to see the top fall. He turns away to be with his children. He has chosen that what he feels right now matters more than proof of what is technically real. The film hands the same choice to us: keep demanding an answer, or accept that the feeling is the answer.