Differences, contrast, they are the very things to separate suffering from bliss. It is a fantabulous demonstration about deconstructionism.
If the real world becomes perfect, fitting in all the dreams once described by human being, it wouldn't satisfy people. In other words, a world can not be a blissful place in itself, because bliss is less an outside reality than an estimate of the inner reality, a subjective judgment, a mental state.
So when there's nothing bothering people, they would for sure have impulses to create a troubled world to experience as a counterpart to make them believe that they are leading a life deserving to be appreciated and grateful.
In the end of the film, the hero chose to live in a horrible world not for the sake of suffering but of the happiness from being cared and loved by his fake daughter which is constantly strengthened by the drastic contrast of a simultaneous existing evil environment. It reminds us that not only the comparison of the opposite feelings is the foundation of forming a feeling of bliss, but also the tight entanglement of them can make the bliss much more blissful.
Just record some inspired dialogues:
The world is but lights bouncing around your neurons. It is a metaphor about the subjectivity of the world, the affirmation of the inner reality.
The talking about the hell, about the people in hell pretending to be suffering.
The metaphor about the tortoises piling up endlessly.
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