The central theme of Shaw's play, The Man of Destiny, is illustrated in the title: destiny hinges upon single remarks and occurrences that turn of the tides of life. Shaw illustrates this theme in the dual of wills between General Bonaparte and the Lady over who will possess the mail dispatched to Bonaparte and, more importantly, who will possess knowledge of the contents of one particular letter. The Lady, while in disguise, stole Bonaparte's mail while it was en route to him in order to liberate a letter written by Josephine to her paramour Director Barras, which was maliciously forwarded to Bonaparte with evil intent toward Josephine. In this willful dual, Shaw illustrates that Bonaparte has several chances to change the course of his destiny by how he does or does not react to the situation and to the words the Lady speaks. A pivotal example of this is when she, almost overpowered by Bonaparte's efforts to keep control of his newly gained mail, says:
LADY (springing up with a bright flush in her cheeks). Oh, you are too bad. Keep your letters. Read the story of your own dishonor in them; and much good may they do you. Good-bye. (She goes indignantly towards the inner door.)
This line, and one that precedes it in the play, are two pivotal lines as they clearly open Bonaparte's choices to him and open his destiny to change of course. The other line, also spoken by the unnamed Lady, is:
LADY. Nothing— (He interrupts her with an exclamation of satisfaction. She proceeds quietly) except that you will cut a very foolish figure in the eyes of France.
In the midst of their dual of wills, sometimes slightly physical but mostly a dual of wits, in this second line the Lady speaks directly to the center of Bonaparte's inner motivation, which is his ambitions for his future position in the "eyes of France.” This ambition is alluded to by Giuseppe, the inn keeper, in a line in the first scene: “GIUSEPPE: I shall enjoy looking on at you whilst you become Emperor of Europe,.” The Lady’s "quietly" delivered warning and remonstrance makes Bonaparte take notice because he realizes that if he cuts "a very foolish figure" at this early stage of his career, he will inevitably fail in his ambitions to rise in power.
Later in the play, Bonaparte has gained possession of the letters; the focus of the dual of wills shifts to preventing him from keeping and reading the one particular letter written by Josephine. When Bonaparte has almost won, the Lady reacts in fiery indignation and is on the verge of storming out when she sends another verbal arrow zinging to Bonaparte's ambition. She says: "Read the story of your own dishonor in them." Dishonor is quite a bit worse than cutting "a foolish figure." If cutting a foolish figure could hinder Bonaparte's ambitions, then dishonor could do much, much worse things to his career and ambitions.
Three final things are of particular interest. Firstly, Giuseppi foreshadows the challenges between Bonaparte and the Lady in the opening scene in the line:
GIUSEPPE. We are all cheerfully at your excellency's disposal, except the lady. I cannot answer for her; but no lady could resist you, General.
Secondly, the Lady presents moments to Bonaparte during which his choices might change his destiny. Thirdly, the interesting situational irony of the play is that, while the Lady's effort is to save Josephine's destiny, the effort presents Bonaparte's own destiny into his hands to preserve or alter.