As in everything else, Reynaud looks at Armande's birthday party as a celebration of gluttony and indulgence. He believes it is a mistake - not only because the old woman is very old and sick - but because it is neither edifying to the body or to the soul. In his words,
Don't you care? Don't you care that she's killing herself with gluttony? (Chapter 28)
Vianne on the other hand, was concerned at first with Armande's plans for such a lavish birthday. She too, realizes Armande's precarious health situation - and is reluctant to encourage her in making it worse. But then she realizes that Armande knows she's going to die.
I understand her situation. Why should she struggle to preserve for any longer a condition doomed to this inevitability? (Chapter 34)
Ultimately, the biggest difference between Reynaud and Vianne is their perspective on living. Reynaud believes life must be painful, difficult, uncomfortable, a constant sacrificing of one's desires and pleasure, in order to obtain spiritual blessing and reward. He considers that he receives this blessing through the selflessness on earth and certainly looks forward to more blessings in the afterlife. Vianne on the other hand, does not consider the afterlife at all. She believes life is for living, as full of pleasure as possible. She celebrates everything. She seeks to bring out the best in people by allowing them to indulge in personal pleasure and happiness. In the end, her decision to help Armande in the birthday party has nothing to do with herself - but everything to do with Armande's last wishes for one final night of being surrounded by good friends, family, good food and fun.