Its title, as the author explains in the prologue, is taken from the archaic sense of the word that means "whim", "quirk", "obsession", or even a snatch of music (see earworm).

In this craft she sees what she describes as a divine revelation of heaven ("June Eternal") and the Shaker Trinity (Father, Son, and female Holy Spirit or "Mother Wisdom").

The mystery of Bartholomew's disappearance is never solved, and Ayscough surmises that he committed suicide out of guilt from his disobedience to his father in the matter of an arranged marriage.

The novel also examines the nature of history, historiography, and criminal justice, as Ayscough represents the historian/judge trying to create a coherent narrative out of problematic testimonies.

The power struggle between Ayscough and Rebecca to create the narrative of the past problematises the objectivity of history, making it subordinate to interests of social class and gender.

In the end, Fowles uses Rebecca and Ayscough as representatives of two classes of people, one subjective, intuitive, mystical, artistic (i.e., "right-brained"); the other objective, analytical, and judgmental (i.e., "left-brained").

Finally, Fowles explicitly positions A Maggot in an era which, he claims, saw the beginning of modern selfhood (see self (psychology), self (philosophy), individual).

Rebecca is a prototypical modern individual experiencing the difficulty of breaking free from the restraints of society and convention to be radically self-realized.