Scene 6 depicts Joan's trial. When the inquisitor explains to an indignant Courcelles that he has reduced the charges from sixty-four counts to twelve, he uses verbal irony that at once cushions Courcelles's ego and makes him appear ridiculous to the audience:
Master de Courcelles: I am the culprit. I am overwhelmed with admiration for the zeal displayed in your sixty-four counts; but in accusing a heretic, as in other things, enough is enough. Also you must remember that all the members of the court are not so subtle and profound as you, and that some of your very great learning might appear to them to be very great nonsense. Therefore I have thought it well to have your sixty-four articles cut down to twelve—
If we are to take the Inquisitor at face value, he thinks it is "admirable" that Courcelles has come up with so many counts on which to charge Joan for heresy. He is simply worried that other people in the courtroom are not as smart as Courcelles and will be unable to see the difference between different charges. He is protecting Courcelles from being accused, by other members of the court, of spouting nonsense.
Reading between the lines, the Inquisitor is only pretending to admire Courcelles. In fact, he is insulting him. "Enough is enough," he says. Ultimately, all the charges amount to the same thing: Joan is an accused heretic. They only need so many reasons to burn her. The Inquisitor does not name which members of the court are less "subtle and profound" than Courcelles. What he really seems to mean is that there is no meaningful distinction between a number of the charges Courcelles has drawn up. They are redundant, and Courcelles needs to learn to edit. Suggesting that some unnamed member of the court might mistake the longer charges for nonsense is a backhanded way of saying that they are, in fact, nonsense. The verbal irony in this moment demonstrates a double standard in the Church: Courcelles's "zeal" is more over-the-top even than Joan's zeal for her cause, and yet she is the only one on trial.
In Scene 6, Joan uses verbal irony to respond to Courcelles's accusation that she must be a witch:
COURCELLES. When you were left unchained, did you not try to escape by jumping from a tower sixty feet high? If you cannot fly like a witch, how is it that you are still alive?
JOAN. I suppose because the tower was not so high then. It has grown higher every day since you began asking me questions about it.
Courcelles is embellishing the truth. Joan really did try to escape. He uses this escape attempt against her not as evidence that she is defiant of her punishment but as evidence that she is a witch. After all, he asks her, how else would she have been able to survive a 60-foot jump? She must be able to fly, which would make her a witch. In order to refute this conclusion, Joan tries to answer Courcelles's question. As she always does, she takes what he says at face value. If the tower is 60 feet high, she suggests, it must have grown. In fact, she tells him, the tower has been taller every time he has asked her about it.
Of course, the tower is not actually growing. Instead, Courcelles is reporting it to be taller and taller each time he mentions it. What Joan means implicitly is that Courcelles is lying, but what she says explicitly is that this whole misunderstanding is the tower's fault. This moment of verbal irony is one of several that suggest that Joan might not be so naive as she acts. Her naivety and insistence on engaging in good faith in every argument might be a strategy she cultivates to point out others' shortcomings. If Joan were to say outright that she is not a witch, it would be her word against Courcelles's. Instead, she uses irony to make it clear that he is not the honest and upstanding Christian he pretends to be.
In the Epilogue, Ladvenu tells Charles that Joan has been cleared of all charges. He uses hyperbole and a hint of verbal irony as he reassures Charles that he wasn't crowned by a heretic:
CHARLES. Good. Nobody can challenge my consecration now, can they?
LADVENU. Not Charlemagne nor King David himself was more sacredly crowned.
CHARLES [rising]. Excellent. Think of what that means to me!
Ladvenu compares Charles to two of the most legendary kings. Charlemagne was an emperor who united most of Western Europe for the first time since the Western Roman Empire had fallen to Byzantine rule; Charlemagne was the first Western Roman Emperor in three centuries, and he launched a massive campaign to spread Christianity throughout Europe. King David is an even more significant religious figure. In the Bible, he is most famous for his rags-to-riches ascension after he kills the giant Goliath, proving himself worthier to rule than the neglectful King Saul. Ladvenu is being hyperbolic in his comparison. It would be nearly impossible for anyone to be as "sacredly crowned" as these larger-than-life figures. By invoking them, he reassures Charles that his crown is as safe as safe can be.
But Shaw, if not Ladvenu himself, is being ironic as well as reassuring. Charles VII is not an especially legendary king—this much Shaw and his audience know. Most of his notable successes were in fact Joan of Arc's successes. On its surface, the statement that "Not Charlemagne nor King David himself was more sacredly crowned" means that Charles VII's crowning was as sacred as that of the most important kings in history and mythology. On a deeper level, the line means that none of these kings were sacredly crowned. Or, if they were, to be sacredly crowned does not mean much of anything.
