How does the duel expose the vanity and cowardice of the Vicomte in "A Coward"?
Moving in high society and possessing "a certain inborn elegance, an air of pride and nobility" that makes him a favorite with women and an object of "smiling hostility" by men, the Vicomte de Signoles is an accomplished swordsman and a great marksman with pistols. So, one evening when he invites two couples to join him for ice cream, and one of the ladies is unnerved by a man's staring at her, he immediately reacts, although the husband of the woman says,
"Nonsense! Don't take any notice of him. If we were to bother our heads about all the ill-mannered people we should have no time for anything else."
Nevertheless, the vicomte is quick to reprimand this man who stares at the woman whom he has invited to join him and have ice cream. In his vanity, the vicomte sharply slaps the man when he utters a foul word. Then, "[E]very one rose to interfere." But, compelled by his bravado, the vicomte exchanges his card with his foe and a duel is arranged.
Having returned home, the vain man is beseiged with doubts. In his imaginings, he considers that the man may back down if pistols become the weapon for the duel,
With pistols he would seriously risk his life; but, on the other hand, he might come out of the affair with flying colors, and without a duel, after all.
And, he has misgivings about using pistols. As he speaks aloud, he is unnerved by the sound of his own voice. Later, while he tries to sleep, he is tortured by his thoughts, and awakened by his doubts, "Is it possible to be afraid in spite of one's self?"
He cannot admit to himself that he is cowardly, but the vicomte does consider the consequences to his social standing, his reputation, if he quakes at the moment that he must shoot. What will be thought of him? Seeing that the pistol has a bullet in it, the Vicomte chooses to kill himself rather than be shamed in his society. He is an orphan; no one will feel his shame after he is gone. He makes no last will; his death will seem an accident; perhaps people will think he was cleaning the gun.