Yes, it fully can write a dissertation, which is why I think, as educators, we have to embrace it. Our students will be using it to write papers completely, and we won't have any idea. There's not a plagiarism detector capable of detecting this kind of "writing" yet. I'm not using premium yet, but am using the free version. It's all in how you ask the question, then how you give revised instructions from there. It's fully possible right now.