An argument could be made that Archer is underestimating May's capabilities. The very fact that she knows about his old affair is an indication that she is not as ignorant as Archer suspects. May also has some very perceptive ideas as to why Archer wishes to marry her so soon. Archer explains that is he were in love with another woman he would not be in such a hurry to marry May. May responds insightfully that this would be one way to settle the question: if Archer was indecisive, he might feel that an important action like marriage would decide the question for him. While May sincerely does not want her happiness to come at an expense to Archer's former mistress, she also has personal motivations for finding out if her fiancé is emotionally or physically tied to another woman.
Medora Manson, who makes her appearance in Chapter 17, is an interesting character not only because of her eccentricities, but also because of her tenuous relationship to Old New York. As a Manson, she is connected by blood to some of the most influential families. However, she is considered a hopeless cause because of her odd, faddish ideas and her multitudinous husbands. Medora, then, is forced to remain on the edges of good society, where her eccentricities can be more easily ignored. But for all of her own questionable qualities, she has the practical understanding of Ellen's marital problems that Archer lacks. After Archer proclaims dramatically that he would rather see Ellen dead than return to her husband, Medora forces him to reflect upon the difficult options Ellen faces. Either she can return to a boorish husband, remain married and separated in New York where she will be courted by men looking for a mistress, or she can divorce and cause great amounts of gossip.
Ellen, too, must force Archer to look at the practical side of things. After he expresses his love for her, he impetuously declares the only logical thing for him to now is to break his engagement with May. Ellen replies, "You say that because it's the easiest thing to say at this moment—not because it's true." She further deflates Archer's bubble by remarking that it was he who taught her to sacrifice her own wishes if they caused pain to anyone else. That following his advice means that they can never be together is a great irony, but Ellen pushes Archer to both acknowledge and accept this irony.
Wharton also demonstrates her gift for irony by the way she constructs the narrative at the end of Book One. The Age of Innocence begins in the style of a novel of manners, in which a young unmarried protagonist must encounter all the tribulations involved with falling in love and getting married. The novel of manners usually ends with the happy marriage and settling down of the protagonist. By placing this marriage in the middle of the novel instead of the end, and by describing such a marriage as imprisoning, Wharton radically alters the plot structure of the novel of manners and gives the idea of a happily-ever-after ending a sense of bitter irony.