Others see the dissertation as an opportunity for their students to make definitive statements and establish their places in the discipline. This puts the dissertation more in the category of a monograph or book, publishable without further research. From the beginning, it is important to understand where your dissertation is expected to fall within this spectrum. Overall, the dissertation is an effort of will and self-discipline. The scholar's work is never finished.
Good scholarship produces questions along with answers.
With luck, your dissertation topic will serve you in good research stead for the rest of your life. You don't have to answer all the questions now. In fact, you don't want to answer all the questions now, even if you could. What you want to do is put your research in a coherent form that will make clear the state of the question and your contribution to it at a particular point. Then adhere to it.