A number of themes or concepts are readily apparent in this play:
love marriage revenge hatred bastard deception / treachery faith envy
Of course, as he does in many of his comedies, Shakespeare comments on the nature and folly of love. And such comments represent his main comment or theme for his play.
Yet the reader should not overlook two other significant concepts in the play. The first regards eavesdropping. In his comedy intelligent people eavesdrop and believes the lies that they overhear; but when villains or fools eavesdrop, they learn the truth. Shakespeare could be warning people about eavesdropping, but actually it is not that simple. When Beatrice and Benedick overhear Hero and Don Pedro and the others in the garden, they do believe in the lies created by Pedro and his schemers. Yet the lies actually cover up a hidden truth, and so the eavesdropping in this instance turns out to be a positive act. Yet, when Don Pedro and Claudio eavesdrop on Borachio and a woman whom they think is Hero, the result is not only negative but nearly quite disastrous. So, eavesdropping can be either positive or negative.
The use of eavesdropping, though, contributes to the merriment of the play and the carnivalesque atmosphere. Misunderstanding, confusion, lies, and false identities are features of both the eavesdropping scenes and of the play overall.
The second concept worth the reader's notice concerns chastity. Dating back to the Middle Ages, a woman's virtue depended on her chastity. If she is not chaste, she has no virtue, no honor. She would be ruined, and that ruin would reflect on her entire family. Claudio's accusation against Hero may not seem to be so significant to modern audiences. But Renaissance audiences would understand the severity of Claudio's remark. They would understand that a noblewoman or girl with a high position in society would lose everything by such a remark. Claudio calls Hero a "rotten orange" to express his disgust. Although such a remark would be practically meaningless today, in Shakespeare's time it was a loaded expression. Like a rotten piece of fruit that is useless, an unchaste girl would also be considered useless and of no value. She could not get married. She could never recover her lost honor.