College English: Essay on the Oedipus Plays or Robert Browning

Hey all, I've got a 6 page essay due next Tuesday and I'm having trouble choosing a thesis. We can write about anything we've covered so far this semester and I've narrowed it down to either writing about Sophocles's Oedipus Plays or Robert Browning's poems (My Last Duchess and The Last Ride Together). Anyone have any possible essay topics I could work with regarding either of these works? I was planning on writing about fate versus free will in the Oedipus Plays but found it hard to keep the paper from straying into the philosophical realm which made it particularly hard to write. I'm open to any and all ideas. Thanks for any help you can offer!