One of the main themes in Cosi, is the central idea of personal growth. All characters experience growth, however, Lewis' personal growth is the most significant as his simple dialogue states "no one can sing" exemplifying his negatively towards the patients. This is juxtaposed to his dialogue. "This comes first" when Lewis begins to see the play as his top priority. His transformation is outlined through Lucy's dialogue "Working with these people has changed you." showing Lucy's thoughts concerning Lewis. Lewis' inner journey has provided him with a new understanding of not only himself but the world around him. It is Nowra’s portrayal of Lewis, whose personal growth through the play exemplifies the sympathetic nature of humanity, which suggests the ability to care for others, and to valiantly defend worthwhile causes is an indispensable human characteristic. Initially portrayed as lacking assertiveness, Lewis’s progression throughout the play, both in terms of developing confidence in directing and a rejection of contemporary values, suggests people can be caring and can expect consideration from others.
Another theme is Cosi is to do with the nature of madness. The characters are not what you expect from a patient in a mental institution. Roy is extremely articulate and Doug is very witty. Although all the patients have problems