To decide on a thesis statement, what you will first need to do is understand exactly how Shakespeare has characterized Viola. We gain an understanding of her characterization by analyzing the things she does and says. Below are a couple of ideas to help get you started.
One of Viola's greatest assets is her resourcefulness. When she arrives in Illyria after having survived a shipwreck, she arrives as a now orphaned wealthy noblewoman, believing she is all she has left of her family. Being both wealthy and all alone in a foreign country puts her in a very vulnerable position. Knowing that she is now vulnerable and must fend for herself, she comes up with the resourceful plan of disguising her identity. At first, she decides to disguise herself as a servant in Olivia's household, but when the sea captain warns it would be impossible for her to do so due to the fact that Olivia is forbidding anyone new from entering her household since her brother's death, Viola is next resourceful enough to think of disguising herself as a eunuch and go to work in Duke Orsino's court. While her resourceful decision to disguise herself does cause some problems, Viola was also very right to fear for her safety, and her solution certainly does serve to protect her, much more so than she could have done on her own as a woman.
Viola is also recognized for her wisdom. She is the first character to realize the play's conflicts, particularly her own involvement in the conflict, such as the fact that Olivia has fallen in love with her as Cesario while she, Viola, is in love with Orsino. More importantly, she realizes one of the play's most central themes, which is the dangers of deception. We observe her realizations concerning deception just after she grasps that Olivia has fallen in love with, as we see in her line, "Disguise, I see, thou art a wickedness / Wherein the pregnant enemy does much" (II.ii.26). Her understanding of both the play's conflicts and the central theme make her one of the wisest characters of the play.
Hence, if we were to write a thesis using these two analyses of her characterization, we could create something like this:
- Shakespeare characterizes Viola as resourceful and wise.