And what would you write about?
Keep it reasonable (as in, it would reasonably function as an actual prompt).
I'd love to get an essay about the existence of free will. If you know me well, you'll know I could rant all day on the Butterfly effect, Chaos Theory, fractals, statistics, and so much more to back my claim that we don't have free will. It is, after all, my favorite thing to rant about.