"It is necessary to create constraints, in order to invent freely. In poetry the constraint can be imposed by meter, foot, rhyme, by what has been ca… - Umberto Eco

This has nothing to do with realism (even if it explains also realism). A completely real world can be constructed, in which asses fly and princesses are restored to life by a kiss, but that world, purely possible and unrealistic, must exist according to structures defined at the outset (we have to know whether it is a world where a princess can be restored to life only by the kiss of a prince, or also by that of a witch, and whether the princess's kiss tranforms only frogs into princes or also, for example, armadillos).

We've got to help each other, seeing as God doesn't help us. Do you see how great Jesus' idea was? Imagine how much it must have irritated God. Forget the devil, Jesus was the only true enemy of God, and he's the only friend us poor wretches have.

There, Master Niketas,’ Baudolino said, ‘when I was not prey to the temptations of this world, I devoted my nights to imagining other worlds. A bit with the help of wine, and a bit with that of the green honey. There is nothing better than imagining other worlds,’ he said, ‘to forget the painful one we live in. At least so I thought then. I hadn’t yet realized that, imagining other worlds, you end up changing this one.

When nature fails, we turn to art.