What is the theme in Bright Lights, Big City by Jay Mclnerney?

Moral relativism is at the core of this book. The narrator gets lost in the ambiguity of moral relativism. With the breakup of his marriage and the death of his mother, the narrator flounders in an unsteady world with no known boundaries of behaviour, sexuality or pleasure seeking. He longs for a more sedate existence with healthy routines and normal, home-cooked food. What he really longs for is the moral certainty of a world that no longer exists. It's the world his parents grew up in, where family, work and faith formed a trinity around which all lives revolved.