in love with him (even when it should be apparent that Olivia is in love with Cesario). Particularly noteworthy here is how he is tricked into presenting himself in a manner which Olivia herself is disposed to detest (and one would think, being her steward, he would not have been so ignorant about these kinds of details).

One can point also toward Orsino and his own one-sided pursuit of Olivia, or in Olivia's own case, her pursuit of Cesario, with that startling turn of fortune by which she mistakes Cesario (who is in truth a disguised Viola) for Viola's twin brother and ends up marrying the wrong person. In all of these cases, we have characters swept up in emotions while remaining willfully blind as to the realities of the people they would claim to love.

This is actually what makes Orsino's relationship with Viola so interesting: Orsino knew her first as Cesario (and indeed, for all that one can point out how rapidly he switches his affections from Olivia to Viola, it is at the same time worth noting that their friendship had been a very close one, with deep ties of affection, long before he learned the truth of Viola's deception). In Cesario, he had a close and highly trusted friend, someone he knew as a person, rather than just as an object of affection.

One of the dominant love themes in Twelfth Night is the arbitrariness or foolishness of love. We especially see both the arbitrariness and foolishness of love with respect to both Duke Orsino and Oliva. Duke Orsino proves to be foolish with respect to his persistent obsession over Olivia. He is so obsessed with her that he relentlessly pines for her, visualizing himself as a hart, or deer, being hunted by his emotions. Even the fact that she rejects him due to being in excessive mourning over her brother's death makes him pine for her even more. His line of reasoning is that if she can love a brother so deeply, how much more would she love a man she was in love with?Olivia portrays the theme of both the arbitrariness and foolishness of love first through her rejection of Orsino and then through falling for Viola as Cesario. Olivia really does not have a rational reason for rejecting Orsino, especially considering she admits she knows him to have an exceptional, noble character, as we see in her lines:

Your lord does know my mind; I cannot love himYet I suppose him virtuous, know him noble,Of great estate, of fresh and stainless youth;In voices well divulged, free learn'd, and valiant. (I.v.242-245)

These lines actually describe Orsino as quite a great catch; therefore, she is being portrayed as foolish for rejecting him. Not only that, she falls for Cesario who, based on Malvolio's descriptions of her, looks absolutely nothing like a real man, but more like a cross between a boy and a man. Hence, she has arbitrary reasons for preferring Cesario, showing us again the theme that love is both foolish and arbitrary.

The title of this play refers to a holiday during the time when people could feast and act in ways that were opposite to their usual personalities.  It was a way to let loose of general worries and daily routines and adopt, for a time, an alternate persona.

The characters in this play seem to have adopted this attitude even though they do not realize it.  Viola adopts the persona of her twin and pretends to be a man, while her actual twin.  Olivia, who spurns the duke in favor of Viola/Cesario, parallels the Duke's ultimate attraction to Viola.  The world, like the intent of the holiday, is turned upside down.  Of course, things settle down, and two, happy couples emerge at the end of the play, devoid of disguise.

The idea of donning a disguise or playing a role is attractive as a way of forgetting one's daily life.  This holiday, and the play, celebrates that.

Though Shakespeare's play is infused with delightful humor, its main theme arguably is the nature of love: who has it, who wants it, who deserves it. For example, Malvolio loves Olivia, but he will never have her and his character, "an affectioned ass" does not deserve her. As for the Duke, he happily gives up the Countess to the newcomer whe he learns that his 'boy" is a lovely maiden who will wed him. Sir Toby marries Maria for her wit, and in the end, it is only Malvolio who is unhappy, both for himself and envious of others who have fallen in love (love that is reciprocated.)

The one dominant theme underlying both the plot and subplot of Twelfth Night can be gleaned from the title of the play and more importantly the subtitle, Twelfth Night; or, What You Will. To understand the meaning of the title and how it connects to the dominant theme, one must first understand the traditions surrounding the Twelfth Night holiday, other wise called The Feast of Epiphany. Epiphany fell on the twelfth night after Christmas day, which marked the day that the Magi, or three Wise Men brought their gifts to baby Jesus. While one might expect an Epiphany celebration to reflect on Christmas traditions, in Elizabethan England, it was actually apparently a "time when excess and license were expected to run rampant" (eNotes, "Twelfth Night: Themes"). Shakespeare even wrote the play for an Epiphany party being held at one of the Inns of Court in 1602, and that particular party was apparently known to be "absolutely secular and even quite bawdy" ("Shakespeare's Twelfth Night"). Epiphany celebrations, especially the one this play was written for, were times of "masques, revels, defiance of authority, and general foolishness" ("Shakespeare's Twelfth Night"). Epiphany was also a "time of merry-making, of hard drinking, and of romantic (or lusty) pursuits" ("Themes"). Shakespeare's play perfectly illustrates the nature of the holiday, as well as human nature as exhibited during the holiday, which brings us to his subtitle, What You Will, meaning "take what you will [from this play]." On the surface, Shakespeare's play seems to be a nice comic love story, but on a deeper level, it is a portrayal of the foolishness of human nature, especially human nature displayed on wild, lawless nights. Hence, the central underlying theme in Twelfth Night is the foolishness of man.

We see foolishness exhibited in Duke Orsino's obsession with Olivia; in Olivia's obsessive, prolonged grief over her brother's death; in Maria's plan to humiliate Malvolio; in Sir Toby and Sir Andrew's drunken, bawdy behavior; and even in Malvolio's self-righteous behavior and arrogance. The only character who does not exhibit foolish behavior is ironically Feste the fool, or court jester. Feste is the only character who makes insightful commentsabout human nature, such as pointing out that Olivia is truly the fool for grieving so severely over the death of a brother whose soul is in heaven, as we see in his lines, "The more fool, madonna, to mourn for your brother's soul being in heaven. Take a way the fool, gentlemen" (I.v.64-65). He even later insightfully calls Duke Orsino fickle, which indeed proves to be true.