In Much Ado About Nothing, Shakespeare shows that the duality between appearance versus reality is a matter of gender, social class, age, and status.
In terms of gender, Beatrice appears to scorn all men, and Benedict appears to scorn all women. But, with carefully crafted "lies," their friends convince them that "love" destroys all scorn. Or, one could say that Beatrice had always secretly loved Benedick but only appeared to hate him to save face and defend herself as an old maid.
In terms of social class, Dogberry appears to be a blathering idiot, but in reality he is more vigilant in his duty than the Prince and his entourage. He and his watchmen discover the plot against Hero and save the day, not with words (appearances), but with actions (reality).
In terms of age, Leonato and Benedick show the young Claudio the meaning of honor as they defend Hero and Beatrice respectively. Even though he is an old man, Leonato challenges Claudio because he knows that his daughter is honorable. So too does Benedick, at the bequest of Beatrice, challenge Claudio. Each man shows that women's actions (reality) far outweigh what men say (appearances) about them.
In terms of status, Don John takes advantage of the naive Prince and Claudio. He appears to be an honorable man by showing that women are deceivers. This confirms what most men wanted to believe, and so the Prince and Claudio fall prey to Don John's words and the appearance of promiscuity (by Hero's gentlewoman). Even though Don John is a bastard, an illegitimate son who is not to be trusted, the other males place more stock in his reputation than that of the otherwise pure Hero.
All in all, words are used to uphold the appearances of male status, reputation, and sexist double-standards instead of the reality of a world in which women, old men, and lower classes may indeed be honorable.