This scene occurs in Act IV scene 2, when Feste, the clown, disguises himself as Sir Topaz, the curate, and tries to reason with the "lunatic Malvolio." What he does is engage in a series of puns and wordplays to demonstrate that Malvolio, in spite of his protestations, is, in fact, mad, even though he strenuously insists otherwise. At one stage in this scene, Malvolio, being unable to see Feste, is addressed by both Feste and then Sir Topaz as Feste disguises his voice. Malvolio insists that he is sane, stating that he is as "well in my wits" as Feste himself. To this, Feste can only respond by stating that this is proof he is mad indeed:
But as well! Then you are mad indeed, if you be no better in your wits than a fool.
This is typical of the way that Feste bends the words of Malvolio to present him as being mad indeed. Feste seems to do this for a number of reasons. One is that because of his function as a fool, he delights in twisting meanings and words. He does this throughout the play with everybody he meets, and so Malvolio is treated no differently in this sense. Secondly, in some productions he is viewed as primarily a force of chaos in the play, being part of Sir Toby's gang of partygoers who oppose the rule and order that Malvolio represents. There is then a sense in which Feste insists Malvolio is mad and confuses him further deliberately to punish him more and to get his own personal revenge. Lastly, the theme of madness and love is one that is crucial to the play. It is something that is seen in the swiftness with which Olivia falls in love with Cesario, and it can be seen in Malvolio and his courting of Olivia. Feste insists that Malvolio is mad to reinforce the central theme of the play: all humans are mad when it comes to matters of the heart and affections.