Starting point of this work can be founded in the so called “Allegory of the cave”, an allegory used by the philosopher Plato to demonstrate that what people take to be reality would often be an illusion.

In his scenario, Plato imagines that some people have lived chained in a cave all of their lives, facing a blank wall. The people watch shadows projected on the wall by things and people passing in front of a fire behind them. The shadows are as close as the prisoners would take them to be real things (and the echoes to be real sounds). If one of the prisoners is permitted to stand up and glance outside the cave, he would probably not recognize anything: the shadows on the wall may remain more real than reality itself. Inspired by this allegory, "Spirit" evokes the difficult way going from illusion toward reality and truth in the hope of reaching the "last step", serenity. Would it be the eternal quest of the Graal ?