What is the theme in Siddhartha by Hermann Hesse?

Hesse's works are largely confessional and autobiographical and deal with questions of "Weltanschauung," of a philosophy of life. Typically, as in Siddhartha, the individual's search for truth and identity through what Hesse called the "inward journey" is draped around the plot. Siddhartha, the obedient son of a rich Brahman, awakens one day to the realization that his life is empty and that his soul is not satisfied by his devotion to duty and strict observances of religious ordinances.