The novel opens at the opera, aptly introducing the recurring metaphor of performance, or keeping up an appearance of correct and moral behavior, whatever the reality might be. Julius Beaufort is an example of someone who manages to do this until the end of the novel, when he is unmasked and ostracized. Correct dress and customs become the props that hold the performance together. When Beaufort is trying to fool people into thinking that he is being financially tided over, he has his wife appear at the opera with an expensive necklace - which later is revealed to have been borrowed.
A moving leave-taking scene in a play between two lovers who do not express their love becomes symbolic to Archer of his leave-taking from Ellen. The metaphor of performance expresses the fact that Archer and Ellen have had to pretend and not been true to their love.
Archer likens his wedding to the first night at the opera, drawing attention to the unreality of the event - Archer is marrying one woman but loves another. Archer considers his wife bland and dull, and has no idea what, if anything, lies behind the theatre curtain of May's "niceness."
Most of the characters in the novel are playing a part for much of the time, with varying degrees of success. Archer and May play the part of loving spouses, Ellen tries to play the part of a respectable society lady for a while, Mr Welland plays the part of an invalid to protect himself from society's unpleasant aspects, and Lefferts plays the part of loyal husband to hide his adulteries. This is not to say that they are being utterly false to themselves while in these parts, as the parts represent an aspect of themselves. But there is much that they keep hidden and unsaid.
In Chapter 10, Archer likens May to a Kentucky cave-fish, which ceased to develop eyes because it had no use for them. He feels it is his task to remove the bandage from her eyes, but he worries that perhaps, when he asks May to open her eyes and look upon the world, "they could only look out blankly at blankness." In fact, there is an irony behind May's supposed blindness and Archer's assumed role as sight-giver. It transpires that May has all along known more than Archer gives her credit for, including his feelings for Ellen and the sacrifice he made in staying with his wife and family. Archer had little idea of this; he failed to see it. Indeed, Ellen feels he was under an illusion regarding their future prospects together.
So while Archer does see the hollowness of society's mores more clearly than the other characters, there are many things that he misses within the complex world of relationships.
The repressive old New York society put the individual at war with society, and Wharton's military and prisoner-of-war metaphors emphasize this.
In Chapter 33, at the terrifying dinner party May throws for Ellen's departure, Archer feels "like a prisoner in the center of an armed camp." He knows that he has been branded a traitor by May's family. Wanting to escape from his prison, Archer announces that he intends to travel soon. Later, he catches May's glance of "triumph" and knows that she is the victor in an unspoken war against Ellen, with Archer as the prize.
Society relies on complex codes which can only be understood and interpreted correctly by insiders; if one transgresses the code, as Ellen did, one is expelled. Codes belong in the world of espionage and cold war, and Wharton's use of the word highlights society's mistrust of outsiders and imposters, and its readiness to brand people enemies or traitors.
In Chapter 1, Wharton refers to "the inscrutable totem errors" that obsessed both 'primitive' cultures and old New York society. Old New York society considered itself the height of sophistication, and would be appalled to have its conventions likened to those of defunct primitive cultures. But Wharton, who had seen the seemingly solid old New York society melt away by the time she wrote The Age of Innocence, knew they were just as transient and arbitrary. This is brought home in the scene at the museum, where Ellen comments on the artifacts of dead cultures, once important to their owners, now labeled "Use unknown."
Old New York society expected that members of the culture know the details of correct behavior and stick to them. The dinner-party in Chapter 33 is portrayed as a ritual exclusion from the tribe of Ellen, who has transgressed the tribe's customs.