What is the theme in Grendel by John Gardner?

Grendel's relationship with art is a theme in this book. Because Grendel views the world as a mechanical loop, it is very difficult for him to find an emotional link. Seeing the world as a machination doesn’t allow for meaningful connections, and so Grendel often has bouts of extreme loneliness. When the Shaper appears, his music and words fill Grendel with purpose, something he never experienced when the world was mechanized.