Of the idealistic characters in Nostromo, Antonia Avellanos is perhaps the most complex. She begins by idealizing her father Don Jose, moves through a period of both attraction and opposition to the skeptic Decoud, returns to her dying father at the moment of crisis, and appears at the end of the book alongside Father Corbelan agitating for new political ideals.

The key to Antonia's function in the novel is that she is an allegorical character. She stands for pure idealism, idealism as such: optimistic faith in the redeeming power of the dream-ideal. Her back-and-forth affair with Decoud, who sees the dream-ideal as a fatal affliction upon mankind, will constitute the central tension of Part Two, with resulting action that generates most of the plot.