In the novel Fifth Business what is the importance of the theme of sainthood?

In Fifth Business, the importance of the theme of sainthood has to do with two specific characters: Dunstable (Dunstan) Ramsay and Mary Dempster.  

Dunstable Ramsay (who is later referred to as Dunstan or Dunny) has to do with the theme of sainthood due to his study of saints. The irony is that Ramsay is not even a Roman Catholic, but his obsession with saints eventually brings him all over Europe. Ramsay's true interest in sainthood has more to do with the supernatural aspect of sainthood than the religious aspect of sainthood. Ramsay proves this when he begins to pursue magic as a career. As further proof, the reader finds Ramsay comparing the New Testament to the Arabian Nights and comparing Mary Magdalene to mythological archetypes. Dunstable Ramsay finally receives the name of Dunstan after he returns from the war as a crippled hero. As a kind of martyr for the cause, Dunstan's name was taken from a saint who supposedly caused the deformity in the devil's nose. It is at this point that Dunstan's obsession with saints takes over. Dunstan visits shrine after shrine in Europe, writes many books on saints, and is eventually considered a hagiographer. The other irony is that Dunstan does not act very holy, especially when he tries to convince Staunton to take the blame for causing the ill-fated snowball incident from their youth.

Mrs. Dempster, on the other hand, has her "sainthood" thrust upon her by a hard snowball that hits her and causes early labor. Mrs. Dempster already has her marriage to the Baptist minister going for her, and now her sainthood appears confirmed by many strange "miracles." First, Mrs. Dempster uses her "generosity" to give her body to people other than her husband (such as a vagrant). The vagrant then ceases his evil behavior and immediately becomes a missionary. Later, Mrs. Dempster "resurrects" Willy (who is on the verge of death) and eventually appears to Dunstan during the war in a kind of saintly apparition.

The theme of sainthood connects the two characters through the vision on the battlefield during World War I. It is this vision, more than any of the other "miracles," that makes Dunstan believe Mrs. Dempster is a saint. At this moment, Mrs. Dempster joins the throng of saints fueling Dunstan's obsession with saintly holiness.