In the play's first extended conversation, which roughly makes up the first half of Act I, Lady Windermere and Lord Darlington disagree on the value of being seen as good. Whereas Lady Windermere believes it possible to perceive morality in others, Lord Darlington derides people who are good and people who wish to be taken seriously. Employing alliteration, he argues that these people are boring:
Who are the people the world takes seriously? All the dull people one can think of, from the Bishops down to the bores.
This instance of alliteration contributes to the first impression the audience members form of Lord Darlington. Because this conversation occurs so early in the play, it plays an important role in framing significant themes and questions that will return throughout. The conversation also offers important instances of characterization. For example, Lord Darlington's line about the Bishops and the bores encapsulates his worldview. By lumping figures of religious authority with "bores," he shows that he is free-thinking and free-spirited. Darlington's alliterative delivery of this idea shows that he has a lyrical, lighthearted style of self-expression—even when expressing transgressive ideas.
Lady Windermere's responses to Lord Darlington in the same act show that, at least at the play's opening, she has a very different view of things. She also uses alliteration, but to achieve a different effect and to express different ideas. Defending her puritanical inclinations, Lady Windermere critiques the immorality of the period they're living in:
Nowadays people seem to look on life as a speculation. It is not a speculation. It is a sacrament. [...] Its purification is sacrifice.
Lady Windermere's speculation, sacrament, and sacrifice feel very different from Lord Darlington's bishops and bores. Whereas he plays with language to underline that he doesn't care about much, she uses language to express her serious convictions about the world. Their respective uses of alliteration, found in such close succession, reinforce their differing worldviews. In this early conversation, Wilde introduces a tension between flippancy and solemnity that will remain throughout the play.