In Act 1, Part 3, immediately after the scene of Cheveley's confrontation with Robert Chiltern—in which Cheveley initiates her blackmail and the audience learns of the deceitful beginning to Chiltern's career after his sale of insider knowledge of the Suez Canal project—Wilde builds some dramatic irony for the audience by having Lady Markby compliment the Chilterns and their virtues to Cheveley herself:
Lady Markby: Well, dear Mrs. Cheveley, I hope you have enjoyed yourself. Sir Robert is very entertaining, is he not?
Mrs. Cheveley: Most entertaining! I have enjoyed my talk with him immensely.
Lady Markby: He has had a very interesting and brilliant career. And he has married a most admirable wife. Lady Chiltern is a woman of the very highest principles, I am glad to say.
Markby cannot suspect the real reason that Cheveley so enjoyed her talk with Chiltern, nor can she know that Robert’s prestigious reputation has been built upon a criminal business deal, but the audience is well aware—and Wilde therefore stages this interaction with multiple layers of dramatic irony.
At this point in the play, as Wilde begins to reveal the deceit underlying his portrayal of London society, he also begins to call into question the appearances and first impressions of every character. Even Markby’s observation that Lady Chiltern is a woman of “the very highest principles” takes on new meaning as the play progresses: it will be these principles that impede her ability to forgive and accept her husband for his past mistakes, and the fate of their love will rest on the couple’s ability to overcome their shallow notions of status and virtue.
In Act 2, Part 1, Sir Robert Chiltern woefully describes how Baron Arnheim seduced him with talk of power and wealth—talk that ultimately convinced Robert to sell a government secret to Arnheim in order to give momentum to his own political career. With considerable verbal irony, he recounts his experience of Arnheim’s persuasion using the language of philosophy and religion:
With that wonderfully fascinating quiet voice of his he expounded to us the most terrible of all philosophies, the philosophy of power, preached to us the most marvellous of all gospels, the gospel of gold. I think he saw the effect he had produced on me, for some days afterwards he wrote and asked me to come and see him.
In the Christian culture of England at the time of Wilde’s writing, the gospel would have been seen as the message of the opportunity to find salvation through Jesus Christ. Robert’s use of the term "gospel" to describe the avaricious ideology of Arnheim, an ideology that is diametrically opposed to that of the gospel, thereby gains considerable verbal irony: at the point at which he tells this story to Lord Goring, he is consumed with regret over his actions. Τhe effect of this irony, and the tension between Christian virtue and Arnheim’s worldview, is therefore to underscore the religious fervor with which Arnheim spoke of wealth and power. It also shows the pull that Arnheim’s words must have had on Robert for him to be convinced to illegally sell information on the Suez Canal.
In light of Wilde’s own personal ambivalence toward religion, however, this passage may gain another level of irony: in highlighting how Arnheim and Robert both embraced this alternative "gospel," Wilde shows how fickle and arbitrary—if not downright damaging—humanity’s most fervent beliefs can be.
In Act 4, Part 1, Lord Caversham heartily criticizes his son for embodying what Caversham sees as the failings of the younger generation. In a moment of special dramatic irony, he contrasts his son’s behavior with that of Sir Robert Chiltern, who has just given a rousing speech against the Argentine Canal project in Parliament:
Lord Caversham: Do you mean to say you have not read The Times leading article on Robert Chiltern’s career?
Lord Goring: Good heavens! No. What does it say?
Lord Caversham: What should it say, sir? Everything complimentary, of course. Chiltern’s speech last night on this Argentine Canal scheme was one of the finest pieces of oratory ever delivered in the House since Canning.
Lord Goring: Ah! Never heard of Canning. Never wanted to. And did ... did Chiltern uphold the scheme?
Lord Caversham: Uphold it, sir? How little you know him! Why, he denounced it roundly…
Of course, it is thanks to Lord Goring’s moral clarity and his friendship with Robert Chiltern that Chiltern has been able to navigate the potential scandal with the Argentine Canal with such aplomb—but Caversham does not know this and Goring does not let on. Caversham’s criticisms of Goring are thus laden with dramatic irony: Goring is responsible for the very behavior in Chiltern that Caversham so admires.
