Defining Mahony as a "questor" and noting biographical connections with Henry Handel Richardson and her father, Green describes the philosophical structure that appears in the three volumes. Green argues that the main theme of the trilogy is "the psychic war in the human soul between the desire for permanence and the desire for change". Richard and Mary Mahony represent these desires: Richard desires change and Mary desires permanence. These desires are portrayed symbolically as water and earth, respectively, and the comfort of the two characters is dramatized in relation to this symbolic backdrop.