Most stories by J.D. Salinger show concern for spiritual matters, and "De Daumier-Smith's Blue Period" is no exception. Jean, the narrator, belongs to no specific religion. Rather, he seems to be taking what he likes from many different religions. This allows him to form a unique spiritual viewpoint. Jean is a self-proclaimed "agnostic" and "evil-minded monk" (45, 68). What happens when a guy like that gets a crush on a nun like Sister Irma? A mass of conflicting emotions is what happens. At the end of the story Jean comes to believe that letting go and letting people chose their own destinies is a high spiritual position, because it considers the spirits of other people and not just one's own. Did we mention the story is very funny? What's that got to do with Spirituality? Laughter, the novel, suggests, is a powerful medicine for the spirit, not to mention the body.
The dummy in the window of the orthopedic shop mesmerizes Jean because he thinks that even it has a richer spiritual life than he does.
Jean doesn't seem to have a specific religion, but he is a very spiritual person.