Is the heme of a novel more like its message, or its subject?
This is a great question, because the answer is “both”! A story rarely has only one theme. Theme and subject are often interchangeable. So are theme and moral. So to take your Tempest example, there are many themes that we can tease out from the text. One is “the human desire to conquer and exploit.” Another is “the fallacy of colonization.” Another is “the power of spectacle/art (in the play, it’s represented by magic) to move the human spirit.” Another is “complicated family relationships and ways to make them right again.” These are all topics of the play, they are all messages of the play, they are all themes.
