Religious deconstruction
The major theme of the book is religious deconstruction. Several nuns go into the mountains, a symbol for their voyage into personal chaos, where they seek to establish a religious order among the natives. That chaos toward order means that they are constructing something, but as they do this, the already successful religious beliefs of the area permeate their imaginations and they realize that what they are doing prescriptively is in fact a description of mysteries. They begin to gradually change their mind, becoming more honest in their religion.
Sexual desire and religion
The nuns are in a contrast because they are natural women with desires for sex, but they are also committed to a religious oath of celibacy. Through Sister Superior's story, the arch-nun, we see a metaphor for what kinds of situations might lead a woman to those sorts of oaths. For her, religion was an asylum for her processing deep emotions regarding a past lover. That connection between religion and sexuality leads her to a serious sacrifice, and the story makes it clear that she is unsure whether she has the moral courage to continue in that sacrifice, knowing her motives were partial.
Conversion and narcissism
The movie offers a portrait of narcissism being defeated by a culture of already-friendly and sociable folks who are largely not in need of any new-fangled salvation. Their religious setting is operating well for them right now, and so the nuns begin to orbit around their cultural identity as well. In other words, the theme starts with an intention to convert the poor pagan to their salvation, but the nuns are the ones who are saved in their personal lives by opening their minds to other ways of life. In light of the beauty and wisdom they discover, they are suddenly confused about their own religious language.
