Rasselas, or The History of Rasselas, Prince of Abissinia, was originally called The Prince of Abissinia: A Tale, although the title while Samuel Johnson wrote it was The Choice of Life. It is this working title which gives us a clue to the theme of the book: happiness.
Throughout the story, Rasselas, the son of the King of Abyssinia, tries to find happiness. First he does this by attempting to escape the Happy Valley which, as the name suggests, is a “happy” place. However, Rasselas wants to find what he believes to be true happiness, and so he leaves with his sister and begins searching the world. After visiting many places, they eventually realize that they haven’t found it, and they won’t. This reflects Johnson’s belief that happiness is not attainable, at least in the sense that most people are looking for it. Johnson was a religious man, and believed that earthly life could never provide the everlasting peace we are all searching for. Human nature will always prevent us from being content, and therefore we will always be searching for the next thing that makes us happy.