Much Ado About Nothing juxtaposes the honorable with the dishonorable. It also juxtaposes honor with appearances and reality, showing us that the theme concerning honor questions whether or not what seems honorable is truly honorable and vice versa.
Both Don Pedro and Claudio appear to be honorable men and are even celebrated as such with a feast at Leonarto's home. However, both men are very easily duped by the dishonorable Don John. They know perfectly well that Don John is not to be trusted. When Don John first accuses Hero of unfaithfulness, Don Pedro has the sense to say that he does not believe it, as we see in the line, "I will not think it" (III.ii.100). However, both Claudio and Don Pedro allow themselves to be tricked and even declare that they will shame Hero before the congregation at the church. Their behavior allows us to question whether or not they are truly honorable men or if they simply just appear to be honorable. Claudio evidently has a very jealous nature. He is so jealous that he allows himself to be duped by Don John, not once, but twice. The first time happens when Claudio allows Don John to convince him that Don Pedro has turned against him and courted Hero for himself, as we see in Act 2, Scene 1. However, the Prince righted the situation and proved that he had won Hero specifically for Claudio. Since Claudio's jealous nature incites his distrust in his friends, we see that Claudio's honorable nature is really only an appearance, a deception. In reality, his honorableness is questionable.
In turn, Claudio's jealous nature leads him to question Hero's honorableness. He draws a contrast between Hero's name, which represents a virtuous and honorable person, and what he now believes her to truly be, as we see in the lines:
O Hero! what a Hero hadst thou been
If half thy outward graces had been placed
About thy thoughts and counsels of the heart!" (IV.i.103-105).
In other words, Claudio is stating that her looks are more wonderful than her heart truly is. But of course, the audience knows that Claudio has permitted himself to be fooled by a reputably dishonorable man, showing us that Claudio is actually the dishonorable person, not Hero. Hero, who is called dishonorable, actually turns out to be the most honorable character of all of them.
Hence, we see that Shakespeare's theme of honor presents the idea that honor is not always what it appears to be.