What is the theme in The Human Comedy by William Saroyan?

Loneliness is a central theme in this book. The action, characterizations, and narration of the book are all grounded in one central theme, the contention that an unavoidable part of the human experience is a fundamental, inevitable loneliness . In some ways, this is something of an "existentialist" perspective, existentialism being a school of philosophy that contends that the individual human experience of existence is all there is - there is no pre-life, no after life, no spiritual context in which existence plays out or which gives it meaning. In existentialist philosophy, therefore, loneliness is a fundamental and inescapable component of existence.