The plot of Twelfth Night revolves around love and mistaken identity. Shakespeare seems to be using the characters to demonstrate how frivolous and changeable is the very idea of love, particularly through the characters of Sebastian, Viola, Olivia, and Orsino. Each of them is in love with the idea of love, especially Orsino and Olivia. Viola and Sebastian seem to be fairly solid and capable; they both survive a shipwreck which killed many others and are able to make their way in strange territory. This is not to say that they do not have help, but they are still resourceful. On the other hand, Orsino and Olilvia, both upper-class characters used to getting their own way, are clueless about what love really means and are quite happy to simply switch from one partner to another. Viola herself seems to represent a kind of selfless, unconditional love. She has the most solid, realistic perception of life and love of any of the characters in the play. She loves Orsino, but she wants him to be happy, so she agrees to court his beloved for him. Olivia is quite sure that she does not love Orsino, yet she instantly falls for Viola in her disguise as Cesario. Nevertheless, she is happy to take Sebastian in Viola's place. Still, since it is a comedy, all of the main characters are happily married at the end.