One large and looming theme in the play is the idea of the individual in a changing world.  For a great deal of time in literature and in art, we had been told how individuals should cling to their own identities in the face of conformist social orders.  The notion here is that individuals should revel in their difference.  One critical element in the play is that there are moments when it is difficult and downright painful to constantly be the lone holdout against society.  Strip away the Romantic connotations attached to individuality, and one finds a plight where desolation and loneliness does result.  This is painful and Ionesco brings out its particular pain.  This is in no way suggesting that one capitulated and surrender, but rather it highlights the struggle in being different in a world of where everyone is turning into a rhinoceros.  It is difficult to be a human in this setting.  As proven in the ending where there is an affirmation of individualism, it still is  challenge and is a difficult process.