Children of No One

This novel is an exploration of the concept of torture as art. I found it to be a sort of concept piece, an allegory of sorts, rather than a true story. The characters are not flesh and blood and seemed representative of concepts or philosophical positions. Two competing artists, one a sadist, one a nihilist, a wealthy "audience member"---representing us, and a practical workman just doing his job and not thinking about the moral ramifications of anything he does. An experimental and literary work to be sure. Although I was not really captivated by the story line, and maybe I wasn't supposed to be. I did find myself contemplating, and being disturbed by, the overall concept long after I finished the book. I still am, actually.
Torture as art. A repulsive concept. But isn't that the whole idea behind some movies, art and literature? Some horror movies and books qualify. I remember looking at Renaissance paintings of the death of Saint Sebastian, tied to a tree and pierced by arrows, the wounds cruel and realistic, his pain evident on his face.
Why are we attracted to art showing the suffering of others as entertainment. Clearly in this book, the torture that the artists are creating for their viewers is real, whereas in books, art and movies it is merely representative, but conceptually it is still disturbing even if more ethically defensible.
What is the source of this tendency in human nature and why is the suffering of others so appealing in art?