Help with The Scarlet Letter theme(essay)?

Why not write an essay identity and society? That is a major theme throughout the novel. You can use Hester and how she's viewed in society, you can use Pearl, you can use a lot of characters in different ways and it gives you freedom. Or else sin isn't bad either, as long as you're expansive with it you don't have to worry about it being too narrow of a topic. Go with your instinct, if it's something you believe, then it will be easier for you to write an entire paper on it.