Waking Life (2001)

A boy has a dream that he can float, but unless he holds on, he will drift away into the sky. Even when he is grown up, this idea recurs. After a strange accident, he walks through what may be a dream, flowing in and out of scenarios and encountering various characters. People he meets discuss science, philosophy and the life of dreaming and waking, and the protagonist gradually becomes alarmed that he cannot awake from this confusing dream.